xfs: convert xfs_log_commit_cil() to void

Convert xfs_log_commit_cil() to a void function since it return nothing
but 0 in any case, after that we can simplify the relative code logic
in xfs_trans_commit() accordingly.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>