md/bitmap: move printing of bitmap status to bitmap.c

The part of /proc/mdstat which describes the bitmap should really
be generated by code in bitmap.c.  So move it there.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --cc drivers/md/bitmap.c
Simple merge

diff --cc drivers/md/bitmap.h
Simple merge

diff --cc drivers/md/md.c
Simple merge