intel/batch_decoder: decoding of 3DSTATE_CONSTANT_BODY.

intel/batch_decoder: decoding of 3DSTATE_CONSTANT_BODY.

SNB doesn't have a definition of 3DSTATE_CONSTANT_BODY, thats
why we got segmentation fault when used INTEL_DEBUG=bat.
Fixed by adding of 3DSTATE_CONSTANT_BODY into 3DSTATE_CONSTANT
of VS, GS and PS structures.

v2: added definition of 3DSTATE_CONSTANT_BODY to the gen6.xml

Fixes: 169d8e011ae (intel: Fix 3DSTATE_CONSTANT buffer decoding.)
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107190
Signed-off-by: Sergii Romantsov <sergii.romantsov@globallogic.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>