drm/i915: Shuffle the skl+ plane register definitions

Rearrange the plane skl+ universal plane register definitions:
- keep everything related to the same register in one place
- sort based on register offset
- unify the whitespace/etc a bit

v2: Define register contents after all offsets (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240513165909.15234-1-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>