assembler: Make explicit that labels are part of the instructions list

The output of the parsing is a list of struct brw_program_instruction.
These instructions can be either GEN instructions aka struct
brw_instruction or labels. To make this more explicit we now have a type
to test to determine which instruction we are dealing with.

This will also allow to to pull the relocation bits into struct
brw_program_instruction instead of having them in the structure
representing the opcodes.

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

assembler/disasm-main.c

@@ -167,6 +167,6 @@ int main(int argc, char **argv)
     }
 	    
     for (inst = program->first; inst; inst = inst->next)
-	brw_disasm (output, &inst->instruction, gen);
+	brw_disasm (output, &inst->instruction.gen, gen);
     exit (0);
 }