assembler: Update the disassembler code

assembler: Update the disassembler code

From Mesa. This imports a bit more the of brw_eu* infrastructure (which
is going towards the right direction!) from mesa and the update is quite
a significant improvement over what we had.

I also verified that the changes that were done on the assembler old
version of brw_disasm.c were already supported by the Mesa version, and
indeed they were.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>