drm/i915: Cosmetic fix for skl+ plane switch statement

One of the switch cases has the byte order vs. format bits
reversed to all the other cases. Appease the ocd and reorder
them.

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190703200824.5971-6-ville.syrjala@linux.intel.com