Introduce own lock to silence lockdep warning. lockdep validator
makes wrong decision when two similar (&map->mutex) locks were taken
recursively, even those are different mutexes in a two different
drivers. After that patch, functionality remains same, but mutex names
are different. That is a temporary hack, proper solution is make
regmap aware of locked nested locking rules.

=============================================
[ INFO: possible recursive locking detected ]
3.18.0-rc4+ #4 Tainted: G           O
---------------------------------------------
kdvb-ad-0-fe-0/2814 is trying to acquire lock:
 (&map->mutex){+.+.+.}, at: [<ffffffff814ec90f>] regmap_lock_mutex+0x2f/0x40

but task is already holding lock:
 (&map->mutex){+.+.+.}, at: [<ffffffff814ec90f>] regmap_lock_mutex+0x2f/0x40

other info that might help us debug this:
 Possible unsafe locking scenario:
       CPU0
       ----
  lock(&map->mutex);
  lock(&map->mutex);

 *** DEADLOCK ***
 May be due to missing lock nesting notation
1 lock held by kdvb-ad-0-fe-0/2814:
 #0:  (&map->mutex){+.+.+.}, at: [<ffffffff814ec90f>] regmap_lock_mutex+0x2f/0x40

stack backtrace:
CPU: 3 PID: 2814 Comm: kdvb-ad-0-fe-0 Tainted: G           O 3.18.0-rc4+ #4
Hardware name: System manufacturer System Product Name/M5A78L-M/USB3, BIOS 2001    09/11/2014
 0000000000000000 00000000410c8772 ffff880293af3868 ffffffff817a6f82
 0000000000000000 ffff8800b3462be0 ffff880293af3968 ffffffff810e7f94
 ffff880293af3888 00000000410c8772 ffffffff82dfee60 ffffffff81ab8f89
Call Trace:
 [<ffffffff817a6f82>] dump_stack+0x4e/0x68
 [<ffffffff810e7f94>] __lock_acquire+0x1ea4/0x1f50
 [<ffffffff810e2a7d>] ? trace_hardirqs_off+0xd/0x10
 [<ffffffff817b01f3>] ? _raw_spin_lock_irqsave+0x83/0xa0
 [<ffffffff810e13e6>] ? up+0x16/0x50
 [<ffffffff810e2a7d>] ? trace_hardirqs_off+0xd/0x10
 [<ffffffff817af8bf>] ? _raw_spin_unlock_irqrestore+0x5f/0x70
 [<ffffffff810e9069>] lock_acquire+0xc9/0x170
 [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
 [<ffffffff817ab50e>] mutex_lock_nested+0x7e/0x430
 [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
 [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
 [<ffffffff817a530b>] ? printk+0x70/0x86
 [<ffffffff8110d9e8>] ? mod_timer+0x168/0x240
 [<ffffffff814ec90f>] regmap_lock_mutex+0x2f/0x40
 [<ffffffff814f08d9>] regmap_update_bits+0x29/0x60
 [<ffffffffa03e9778>] rtl2832_select+0x38/0x70 [rtl2832]
 [<ffffffffa039b03d>] i2c_mux_master_xfer+0x3d/0x90 [i2c_mux]
 [<ffffffff815da493>] __i2c_transfer+0x73/0x2e0
 [<ffffffff815dbaba>] i2c_transfer+0x5a/0xc0
 [<ffffffff815dbb6e>] i2c_master_send+0x4e/0x70
 [<ffffffffa03ff25a>] regmap_i2c_write+0x1a/0x50 [regmap_i2c]
 [<ffffffff817ab713>] ? mutex_lock_nested+0x283/0x430
 [<ffffffff814f06b2>] _regmap_raw_write+0x862/0x880
 [<ffffffff814ec90f>] ? regmap_lock_mutex+0x2f/0x40
 [<ffffffff814f0744>] _regmap_bus_raw_write+0x74/0xa0
 [<ffffffff814ef3d2>] _regmap_write+0x92/0x140
 [<ffffffff814f0b7b>] regmap_write+0x4b/0x70
 [<ffffffffa032b090>] ? dvb_frontend_release+0x110/0x110 [dvb_core]
 [<ffffffffa05141d4>] e4000_init+0x34/0x210 [e4000]
 [<ffffffffa032a029>] dvb_frontend_init+0x59/0xc0 [dvb_core]
 [<ffffffff810bde30>] ? finish_task_switch+0x80/0x180
 [<ffffffff810bddf2>] ? finish_task_switch+0x42/0x180
 [<ffffffffa032b116>] dvb_frontend_thread+0x86/0x7b0 [dvb_core]
 [<ffffffff817a9203>] ? __schedule+0x343/0x930
 [<ffffffffa032b090>] ? dvb_frontend_release+0x110/0x110 [dvb_core]
 [<ffffffff810b826b>] kthread+0x10b/0x130
 [<ffffffff81020099>] ? sched_clock+0x9/0x10
 [<ffffffff810b8160>] ? kthread_create_on_node+0x250/0x250
 [<ffffffff817b063c>] ret_from_fork+0x7c/0xb0
 [<ffffffff810b8160>] ? kthread_create_on_node+0x250/0x250
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>