QcomModulePkg: Add support for Virtual A/B

For Virtual A/B OTA feature, change to
  * add intial support for feature.
  * parse misc partition for virtual a/b merge status.
  * publish snapshot merge status in fastboot variables.

Change-Id: I9eff78c4f4727a500cece1f1ef5922ff366528c5
diff --git a/QcomModulePkg/QcomModulePkg.dsc b/QcomModulePkg/QcomModulePkg.dsc
index 87fbdf5..0cc28a9 100644
--- a/QcomModulePkg/QcomModulePkg.dsc
+++ b/QcomModulePkg/QcomModulePkg.dsc
@@ -128,6 +128,9 @@
   !if $(DYNAMIC_PARTITION_SUPPORT)
       GCC:*_*_*_CC_FLAGS = -DDYNAMIC_PARTITION_SUPPORT
   !endif
+  !if $(VIRTUAL_AB_OTA)
+      GCC:*_*_*_CC_FLAGS = -DVIRTUAL_AB_OTA
+  !endif
   !if $(BUILD_USES_RECOVERY_AS_BOOT)
       GCC:*_*_*_CC_FLAGS = -DBUILD_USES_RECOVERY_AS_BOOT
   !endif