southbridge: Add SPDX identifiers to files missing them

This adds SPDX identifiers to the remaining source files in the
southbridge directory that don't already have them.

Signed-off-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
Change-Id: If74aa82a7c40293198e07e81ceac52bd8ca8ad27
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66500
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/southbridge/amd/agesa/hudson/acpi/smbus.asl

@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: CC-PDDC */
+
+/* Please update the license if adding licensable material. */

src/southbridge/amd/pi/hudson/acpi/smbus.asl

@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: CC-PDDC */
+
+/* Please update the license if adding licensable material. */