intel/decoder: tools: Use engine for decoding batch instructions

intel/decoder: tools: Use engine for decoding batch instructions

The engine to which the batch was sent to is now set to the decoder context when
decoding the batch. This is needed so that we can distinguish between
instructions as the render and video pipe share some of the instruction opcodes.

v2: The engine is now in the decoder context and the batch decoder uses a local
function for finding the instruction for an engine.

v3: Spec uses engine_mask now instead of engine, replaced engine class enums
with the definitions from UAPI.

v4: Fix up aubinator_viewer (Lionel)

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