wait_on_page_writeback() was made GPL only in torvalds/linux@19343b5bdd.
Directly call wait_on_page_bit() without using wait_on_page_writeback()
interface, given zfs_putpage() is the only caller for now.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@osnexus.com>
Closes#8794
bfd5a709e7