soc/amd/stoneyridge: Static constify smi_sources

smi_sources is a file local array of constants.

Change-Id: I431f181449a591ccaf8395f01a84c8e006a29b52
Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-on: https://review.coreboot.org/25814
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/amd/stoneyridge/smihandler.c

@@ -186,7 +186,7 @@ int southbridge_io_trap_handler(int smif)
  * Table of functions supported in the SMI handler.  Note that SMI source setup
  * in southbridge.c is unrelated to this list.
  */
-struct smi_sources_t smi_sources[] = {
+static const struct smi_sources_t smi_sources[] = {
 	{ .type = SMITYPE_SMI_CMD_PORT, .handler = sb_apmc_smi_handler },
 	{ .type = SMITYPE_SLP_TYP, .handler = sb_slp_typ_handler},
 };