ext4: clean up some wait_on_page_writeback calls

wait_on_page_writeback already checks the writeback bit, so callers of it
needn't do that test.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --cc fs/ext4/inode.c
Simple merge

diff --cc fs/ext4/move_extent.c
Simple merge