broadcom: Add V3D 3.3 QPU instruction pack, unpack, and disasm.

broadcom: Add V3D 3.3 QPU instruction pack, unpack, and disasm.

Unlike VC4, I've defined an unpacked instruction format with pack/unpack
functions to convert to 64-bit encoded instructions.  This will let us
incrementally put together our instructions and validate them in a more
natural way than the QPU_GET_FIELD/QPU_SET_FIELD used to.

The pack/unpack unfortuantely are written by hand.  While I could define
genxml for parts of it, there are many special cases (like operand order
of commutative binops choosing which binop is being performed!) and it
probably wouldn't come out much cleaner.

The disasm unit test ensures that we have the same assembly format as
Broadcom's internal tools, other than whitespace changes.

v2: Fix automake variable redefinition complaints, add test to .gitignore