intel: compiler: silence compiler warning

../src/intel/compiler/brw_reg.h: In function ‘bool brw_regs_negative_equal(const brw_reg*, const brw_reg*)’:
../src/intel/compiler/brw_reg.h:305:1: warning: control reaches end of non-void function [-Wreturn-type]

Introduced by 8f83eea71e ("i965: Add negative_equals methods").

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/intel/compiler/brw_reg.h

@@ -293,6 +293,7 @@ brw_regs_negative_equal(const struct brw_reg *a, const struct brw_reg *b)
       case BRW_REGISTER_TYPE_UB:
       case BRW_REGISTER_TYPE_B:
       case BRW_REGISTER_TYPE_NF:
+      default:
          unreachable("not reached");
       }
    } else {