drm/i915: Relocate SKL+ NV12 src width w/a

drm/i915: Relocate SKL+ NV12 src width w/a

The SKL+ NV12 src width alignment w/a is still living in an odd place.
Everything else was already relocated closer to the main plane check
function. Move this workaround as well.

As a bonus we avoid the funky rotated vs. not mess with the src
coordinates as this now gets checked before we rotate the coordinates.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181018195921.9898-1-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>