drm/i915/vga: Add more VGACNTRL bits

drm/i915/vga: Add more VGACNTRL bits

Define a pile of extra VGACNTRL bits. We don't really have
any real use for most of these but nicer to have them all
in one place rather than trawling the specs when one wants
to know what's in there.

I will have some real use for the CHV pipe select bits later.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250417114454.12836-3-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>