[PATCH] one ipc/sem.c->mutex.c converstion too many..

Ingo's sem2mutex patch incorrectly replaced one reference to ipc/sem.c
with ipc/mutex.c in a comment.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>