twrp.cpp: Mount vendor_dlkm in fastbootd mode and add property

This property can be used to start scripts or whatever needed like this adsp FW

https: //gerrit.twrp.me/c/android_device_asus_sm84xx-common/+/6564

Change-Id: I0b40e9e6b66041390bb8a99a2fc0a320fd34c8bd
diff --git a/twrp.cpp b/twrp.cpp
index 7a47c5c..39de60e 100644
--- a/twrp.cpp
+++ b/twrp.cpp
@@ -394,7 +394,9 @@
 
 #ifdef TW_LOAD_VENDOR_MODULES
 	if (startup.Get_Fastboot_Mode())
+	android::base::SetProperty("ro.boot.fastboot", "1");
 		PartitionManager.Prepare_Super_Volume(PartitionManager.Find_Partition_By_Path("/vendor"));
+		PartitionManager.Prepare_Super_Volume(PartitionManager.Find_Partition_By_Path("/vendor_dlkm"));
 	KernelModuleLoader::Load_Vendor_Modules();
 #endif