afs: needs sched.h

mips:

fs/afs/flock.c: In function `afs_lock_may_be_available':
fs/afs/flock.c:55: error: dereferencing pointer to incomplete type
fs/afs/flock.c: In function `afs_lock_work':
fs/afs/flock.c:84: error: dereferencing pointer to incomplete type
fs/afs/flock.c:89: error: dereferencing pointer to incomplete type
fs/afs/flock.c:109: error: dereferencing pointer to incomplete type
fs/afs/flock.c:135: error: dereferencing pointer to incomplete type
fs/afs/flock.c:143: error: dereferencing pointer to incomplete type
fs/afs/flock.c:158: error: dereferencing pointer to incomplete type
fs/afs/flock.c:161: error: dereferencing pointer to incomplete type
fs/afs/flock.c:179: error: `TASK_UNINTERRUPTIBLE' undeclared (first use in this function)
fs/afs/flock.c:179: error: (Each undeclared identifier is reported only once
fs/afs/flock.c:179: error: for each function it appears in.)
fs/afs/flock.c:179: error: `TASK_INTERRUPTIBLE' undeclared (first use in this function)
fs/afs/flock.c:182: error: dereferencing pointer to incomplete type

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>