xfs: Convert sync_page_range() to simple filemap_write_and_wait_range()

Christoph Hellwig says that it is enough for XFS to call
filemap_write_and_wait_range() instead of sync_page_range() because we do
all the metadata syncing when forcing the log.

CC: Felix Blyakher <felixb@sgi.com>
CC: xfs@oss.sgi.com
CC: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>