intel/decoder: Engine parameter for instructions

intel/decoder: Engine parameter for instructions

Preliminary work for adding handling of different pipes to gen_decoder. Each
instruction needs to have a definition describing which engine it is meant for.
If left undefined, by default, the instruction is defined for all engines.

v2: Changed to use the engine class definitions from UAPI

v3: Changed I915_ENGINE_CLASS_TO_MASK to use BITSET_BIT, change engine to
engine_mask, added check for incorrect engine and added the possibility to
define an instruction to multiple engines using the "|" as a delimiter in the
engine attribute.

v4: Fixed the memory leak.

v5: Removed an unnecessary ralloc_free().

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>