drm/i915/bios: Define VBT block 15 (Dot Clock Override Table) contents

drm/i915/bios: Define VBT block 15 (Dot Clock Override Table) contents

Define the contents of VBT block 15 (Dot Clock Override Table)

The contents were reverse engineered by intuition. The gen2 stuff
seems solid as I can verify that against real world VBT data. The
gen3 stuff less so as all the gen3+ VBTs I have just filla the
entire block with zeroes.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503122449.27266-16-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>