brw/emit: Fix BROADCAST when value is uniform and index is immediate

Fixes: c74511f5dc ("i965: Introduce the BROADCAST pseudo-opcode.")
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Tried-to-help-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32668>

src/intel/compiler/brw_eu_emit.c

@@ -1936,7 +1936,7 @@ brw_broadcast(struct brw_codegen *p,
        * We will typically not get here if the optimizer is doing its job, but
        * asserting would be mean.
        */
-      const unsigned i = idx.file == IMM ? idx.ud : 0;
+      const unsigned i = (src.vstride == 0 && src.hstride == 0) ? 0 : idx.ud;
       src = stride(suboffset(src, i), 0, 1, 0);
 
       if (brw_type_size_bytes(src.type) > 4 && !devinfo->has_64bit_int) {