New 'addstmmconfig' target to enable StMM in u-boot

Simple target than turns on StMM & optee options in U-Boot. No
guarantees this will work for your platform.

Signed-off-by: Grant Likely <grant.likely@arm.com>

stmm.config

+CONFIG_TEE=y
+CONFIG_OPTEE=y
+CONFIG_OPTEE_TA_AVB=y
+CONFIG_EFI_MM_COMM_TEE=y

top.mk

@@ -116,6 +116,10 @@ ifeq ($(config-targets),1)
 # *config targets only - make sure prerequisites are updated, and descend
 # in scripts/kconfig to make the *config target
 
+addstmmconfig:
+	$(UBOOT_PATH)/scripts/kconfig/merge_config.sh -m -O $(UBOOT_OUTPUT) $(UBOOT_OUTPUT)/.config scripts/stmm.config
+	$(MAKE) -C $(UBOOT_PATH) $(UBOOT_EXTRA) olddefconfig
+
 %config: u-boot/%config
 	$(UBOOT_PATH)/scripts/kconfig/merge_config.sh -m -O $(UBOOT_OUTPUT) $(UBOOT_OUTPUT)/.config scripts/ebbr.config
 	$(MAKE) -C $(UBOOT_PATH) $(UBOOT_EXTRA) olddefconfig