sm8450-common: Simplify AVB flag logic

* AVB's `--flags 3` argument builds a disabled VBMeta with
  disabled hashtree, so no need to set both flags individually.

Change-Id: Ibe9ee322a5af58f13e76d53e18dee49451fe8838

BoardConfigCommon.mk

@@ -81,8 +81,7 @@ TARGET_BOARD_PLATFORM := taro
 
 # Verified Boot
 BOARD_AVB_ENABLE := true
-BOARD_AVB_MAKE_VBMETA_IMAGE_ARGS += --set_hashtree_disabled_flag
-BOARD_AVB_MAKE_VBMETA_IMAGE_ARGS += --flags 2
+BOARD_AVB_MAKE_VBMETA_IMAGE_ARGS += --flags 3
 BOARD_AVB_RECOVERY_KEY_PATH := external/avb/test/data/testkey_rsa2048.pem
 BOARD_AVB_RECOVERY_ALGORITHM := SHA256_RSA2048
 BOARD_AVB_RECOVERY_ROLLBACK_INDEX := $(PLATFORM_SECURITY_PATCH_TIMESTAMP)