ext4: fix error code in ext4_commit_super

We should set the error code when ext4_commit_super check argument failed.
Found in code review.
Fixes: c4be0c1d

 ("filesystem freeze: add error handling of write_super_lockfs/unlockfs").

Cc: stable@kernel.org
Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20210402101631.561-1-changfengnan@vivo.com


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