block: simplify code around releasing bitmaps

block: simplify code around releasing bitmaps

QLIST_REMOVE does not require walking the list, and once the "bitmap"
argument is removed from bdrv_do_release_matching_dirty_bitmap_locked
the code simplifies a lot and it is worth inlining everything in the
callers of bdrv_do_release_matching_dirty_bitmap.

Signed-off-by: Paolo Bonzini <[email protected]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]>
Reviewed-by: John Snow <[email protected]>
Message-id: 20180326104037[email protected]
Signed-off-by: John Snow <[email protected]>