fs/buffer: drop useless return value of submit_bh

submit_bh always returns 0. This patch drops the useless return value of
submit_bh from __sync_dirty_buffer(). Once all of submit_bh callers are
cleaned up, we can make it's return type as void.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/a98a6ddfac68f73d684c2724952e825bc1f4d238.1660788334.git.ritesh.list@gmail.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>