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>

Documentation/mainboard_io_trap_handler_sample.c

@@ -20,7 +20,7 @@ int mainboard_io_trap_handler(int smif)
        switch (smif) {
        case 0x99:
                printk(BIOS_DEBUG, "Sample\n");
-               smm_get_gnvs()->smif = 0;
+               gnvs->smif = 0;
                break;
        default:
                return 0;
@@ -32,6 +32,6 @@ int mainboard_io_trap_handler(int smif)
         * For now, we force the return value to 0 and log all traps to
         * see what's going on.
         */
-       //smm_get_gnvs()->smif = 0;
+       //gnvs->smif = 0;
        return 1;
 }