md/bitmap: fix a might_sleep() warning.
md/bitmap: fix a might_sleep() warning.

commit 8eb23b9f35aae413140d3fda766a98092c21e9b0
    sched: Debug nested sleeps

causes false-positive warnings in RAID5 code.

This annotation removes them and adds a comment
explaining why there is no real problem.

Reported-by: Fengguang Wu <24f7fe9d205c8a9f6ade0c2894e14303ca16087f@intel.com>
Signed-off-by: NeilBrown <1c00aa603bb92d594c03cff60ecf8e63b2a5bcb1@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs