ext4: Don't unlock page in ext4_bio_write_page()

Do not unlock the written page in ext4_bio_write_page(). Instead leave
the page locked and unlock it in the callers. We'll need to keep the
page locked for data=journal writeback for a bit longer.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20230228051319.4085470-5-tytso@mit.edu