cx18: added in cx18_ir_reset_gpio function for lirc_pvr150 like module.  Also
added the ability to reset the IR chip via ioctl like ivtv.  This needs the
mutex to protect gpio_dir and gpio_val in struct cx18 as gpio changes can
come from a few different asynchronous sources now.
Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>