v2.11.x: fixup the intel-signed/sof-arl.ri link

Modify the symbolic link to explicitly link intel-signed/sof-arl.ri
to the intel-signed/sof-mtl.ri binary.

This is first such symbolic link for a intel-signed image,
so better to set a clean first example as this approach is likely
to be copied to handle other similar cases.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>

Author: kv2019i

v2.11.x/sof-ipc4-v2.11.1/arl/intel-signed/sof-arl.ri

@@ -1 +1 @@
-../../mtl/sof-mtl.ri
+../../mtl/intel-signed/sof-mtl.ri