When setting the same GPIO number, multiple IRQ shared requests will be
done without freing the previous request.  It will also try to free a
failed request or an already freed IRQ if 0 was written to the gpio file.

All these oops and leaks were fixed with the following solution: keep the
previous allocated GPIO (if any) still allocated in case the new request
fails.  The alternative solution would desallocate the previous allocated
GPIO and set gpio as 0.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Samuel R. C. Vale <srcvale@holoscopio.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>