drm/i915/bios: handle MIPI Sequence Block v3+ gracefully

The VBT MIPI Sequence Block version 3 has forward incompatible changes:

First, the block size in the header has been specified reserved, and the
actual size is a separate 32-bit value within the block. The current
find_section() function to will only look at the size in the block
header, and, depending on what's in that now reserved size field,
continue looking for other sections in the wrong place.

Fix this by taking the new block size field into account. This will
ensure that the lookups for other sections will work properly, as long
as the new 32-bit size does not go beyond the opregion VBT mailbox size.

Second, the contents of the block have been completely
changed. Gracefully refuse parsing the yet unknown data version.

Cc: Deepak M <m.deepak@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Deepak M <m.deepak@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>