xfs: fix implicit bool to int conversion

try_wait_for_completion returns bool so the wrapper function
xfs_dqflock_nowait should probably also return bool and not int.

Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>