ACPI GNVS: Replace uses of smm_get_gnvs()

Change-Id: I7b657750b10f98524f011f5254e533217fe94fd8
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42849
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/cpu/x86/smm/smm_module_handler.c

@@ -91,6 +91,8 @@ static void smi_restore_pci_address(void)
 
 static const struct smm_runtime *smm_runtime;
 
+struct global_nvs *gnvs;
+
 void *smm_get_save_state(int cpu)
 {
 	char *base;