The raw watermark values are needed when planes are not part of the state,
but this introduced a regression and possibly an overflow when merging
the watermarks because invalid values may end up used. Solve this by calculating
raw watermarks for all levels, and only setting non-zero values when the level
is valid.

Fixes the SNB warning:
   WARNING: CPU: 1 PID: 25405 at drivers/gpu/drm/i915/intel_pm.c:2580 ilk_program_watermarks+0x7b2/0x9d0 [i915]()
   WARN_ON(wm_lp != 1)
   Modules linked in: i915 drm_kms_helper drm bluetooth fuse iTCO_wdt iTCO_vendor_support syscopyarea sysfillrect sysimgblt fb_sys_fops tpm_tis mei_me e1000e snd_hda_codec_hdmi pcspkr tpm mei i2c_i801 lpc_ich snd_hda_codec snd_hda_core
   CPU: 1 PID: 25405 Comm: kms_universal_p Tainted: G     U  W       4.5.0-rc6apollolake+ #462
   Hardware name:                  /DH67GD, BIOS BLH6710H.86A.0160.2012.1204.1156 12/04/2012
    0000000000000000 ffff88009d42b918 ffffffff8143cfab ffff88009d42b960
    ffffffffa0363580 ffff88009d42b950 ffffffff81082746 ffff8800b9a24928
    ffff88009d42ba00 ffff88009d4a0000 0000000000000000 ffff88009d42ba6c
   Call Trace:
    [<ffffffff8143cfab>] dump_stack+0x4d/0x72
    [<ffffffff81082746>] warn_slowpath_common+0x86/0xc0
    [<ffffffff810827cc>] warn_slowpath_fmt+0x4c/0x50
    [<ffffffffa0292862>] ilk_program_watermarks+0x7b2/0x9d0 [i915]
    [<ffffffffa0292cb7>] ilk_initial_watermarks+0x107/0x120 [i915]
    [<ffffffffa02feffa>] intel_pre_plane_update+0x12a/0x190 [i915]
    [<ffffffffa02ffb36>] intel_atomic_commit+0x546/0xd50 [i915]
    [<ffffffffa012c9e7>] drm_atomic_commit+0x37/0x60 [drm]
    [<ffffffffa0217361>] drm_atomic_helper_disable_plane+0xb1/0xf0 [drm_kms_helper]
    [<ffffffffa011cdb4>] __setplane_internal+0x184/0x280 [drm]
    [<ffffffffa012b57a>] ? drm_modeset_lock_all_ctx+0x9a/0xb0 [drm]
    [<ffffffffa012010f>] drm_mode_setplane+0x13f/0x1c0 [drm]
    [<ffffffffa0111b52>] drm_ioctl+0x142/0x590 [drm]
    [<ffffffffa011ffd0>] ? drm_plane_check_pixel_format+0x50/0x50 [drm]
    [<ffffffff811f2744>] ? mntput+0x24/0x40
    [<ffffffff811d28d4>] ? __fput+0x194/0x200
    [<ffffffffa012dec3>] drm_compat_ioctl+0x33/0x40 [drm]
    [<ffffffffa029e1c2>] i915_compat_ioctl+0x32/0x40 [i915]
    [<ffffffff81228d72>] compat_SyS_ioctl+0xc2/0x330
    [<ffffffff810021d5>] ? exit_to_usermode_loop+0x95/0xb0
    [<ffffffff81002d2e>] do_fast_syscall_32+0x9e/0x210
    [<ffffffff8197faf2>] entry_SYSENTER_compat+0x52/0x70

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Testcase: kms_universal_plane
Fixes: d81f04c5 ("drm/i915: Allow preservation of watermarks, v2.")
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/56DEA1FC.8080703@linux.intel.comReviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>