drm/i915/bios: Define VBT blocks 6,7,8 (register tables) contents

drm/i915/bios: Define VBT blocks 6,7,8 (register tables) contents

Define the contents for VBT blocks:
- Block 6 (Extended MMIO Register Table)
- Block 7 (IO Software Flag Table)
- Block 8 (MMIO SWF Register Table)

All of these use the same basic layout, with two known variants:
- data_access_size==0xce -> offset,value tuples are u8,u8
- data_access_size==0x02 -> offset,value tuples are u32,u32

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503122449.27266-13-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>