[PATCH] fat_lock is used as a mutex, convert it to using the new mutex primitive

The fat code uses the fat_lock always in a mutex way (taking and releasing
the lock in the same function), the patch below converts it into the new
mutex primitive.  Please consider this patch for the code.

Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>