intel/brw: Account for reg_unit() in assembler

Use reg_unit() to match the internal representation in brw_reg.
Fixes the assembler tool when targetting Xe2.

Reviewed-by: Sagar Ghuge <sagar.ghuge@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30060>

src/intel/compiler/brw_gram.y

@@ -1502,7 +1502,7 @@ directgenreg:
 	{
 		memset(&$$, '\0', sizeof($$));
 		$$.file = BRW_GENERAL_REGISTER_FILE;
-		$$.nr = $1;
+		$$.nr = $1 * reg_unit(p->devinfo);
 		$$.subnr = $2;
 	}
 	;