xfs: fix xfs_ifree() error handling to not leak perag ref

For some reason commit 9a5280b3 ("xfs: reorder iunlink remove
operation in xfs_ifree") replaced a jump to the exit path in the
event of an xfs_difree() error with a direct return, which skips
releasing the perag reference acquired at the top of the function.
Restore the original code to drop the reference on error.

Fixes: 9a5280b3 ("xfs: reorder iunlink remove operation in xfs_ifree")
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>