drm/radeon: fix ordering in pll picking on dce4+

commit ecd67955fd4c8e66e4df312098989d5fa7da624c upstream.

No functional change, but re-order the cases so they
evaluate properly due to the way the DCE macros work.

Noticed by kallisti5 on IRC.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Julien Cristau <jcristau@debian.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>