drm/i915/bios: Make copies of VBT data blocks

Make a copy of each VBT data block with a guaranteed minimum
size. The extra (if any) will just be left zeroed.

This means we don't have to worry about going out of bounds
when accessing any of the structure members. Otherwise that
could easliy happen if we simply get the version check wrong,
or if the VBT is broken/malicious.

v2: Don't do arithmetic between bdb header and copy
    of the LFP data block (Jani)
v3: Make all the copies up front
v4: Only WARN about min_size==0 if we found the block

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220406133817.30652-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>