intel/genxml: Fix gen10 BLEND_STATE variable length packing

intel/genxml: Fix gen10 BLEND_STATE variable length packing

BLEND_STATE packing was modified to be variable-length in:

 9670124e31 genxml: Make BLEND_STATE command support variable length array.

The initial gen10.xml still had the old, fixed-length style
definition for BLEND_STATE. So gen10_upload_blend_state would
overwrite the packed BLEND_STATE_ENTRYs with its own fixed array
of all-zero entries when packing BLEND_STATE. This caused
BLEND_STATE upload to not work at all.

Fixes: aa416f515a ("i965/genxml: Add gen10.xml")
Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>