ext4,jbd2: fix comment and code style

Fix comment and remove unneccessary blank.

Signed-off-by: Shijie Luo <luoshijie1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200123064325.36358-1-luoshijie1@huawei.com


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