ast2600: Add Secure Boot Controller model

Just a stub that indicates the system has booted in secure boot mode.
Used for testing the driver:

 https://lore.kernel.org/all/20211019080608.283324-1-joel@jms.id.au/

Signed-off-by: Joel Stanley <joel@jms.id.au>
[ clg: - Fixed typo
       - Adjusted Copyright dates ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>

include/hw/arm/aspeed_soc.h

@@ -24,6 +24,7 @@
 #include "hw/misc/aspeed_i3c.h"
 #include "hw/ssi/aspeed_smc.h"
 #include "hw/misc/aspeed_hace.h"
+#include "hw/misc/aspeed_sbc.h"
 #include "hw/watchdog/wdt_aspeed.h"
 #include "hw/net/ftgmac100.h"
 #include "target/arm/cpu.h"
@@ -60,6 +61,7 @@ struct AspeedSoCState {
     AspeedSMCState fmc;
     AspeedSMCState spi[ASPEED_SPIS_NUM];
     EHCISysBusState ehci[ASPEED_EHCIS_NUM];
+    AspeedSBCState sbc;
     AspeedSDMCState sdmc;
     AspeedWDTState wdt[ASPEED_WDTS_NUM];
     FTGMAC100State ftgmac100[ASPEED_MACS_NUM];
@@ -109,6 +111,7 @@ enum {
     ASPEED_DEV_SDMC,
     ASPEED_DEV_SCU,
     ASPEED_DEV_ADC,
+    ASPEED_DEV_SBC,
     ASPEED_DEV_VIDEO,
     ASPEED_DEV_SRAM,
     ASPEED_DEV_SDHCI,