OvmfPkg/PvScsiDxe: Create empty driver

In preparation for support booting from PvScsi devices, create a
basic scaffolding for a driver.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2567
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Message-Id: <20200328200100.60786-2-liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>

OvmfPkg/OvmfPkgX64.dsc

@@ -44,6 +44,11 @@
 
 !include NetworkPkg/NetworkDefines.dsc.inc
 
+  #
+  # Device drivers
+  #
+  DEFINE PVSCSI_ENABLE           = TRUE
+
   #
   # Flash size selection. Setting FD_SIZE_IN_KB on the command line directly to
   # one of the supported values, in place of any of the convenience macros, is
@@ -746,6 +751,9 @@
   OvmfPkg/XenIoPciDxe/XenIoPciDxe.inf
   OvmfPkg/XenBusDxe/XenBusDxe.inf
   OvmfPkg/XenPvBlkDxe/XenPvBlkDxe.inf
+!if $(PVSCSI_ENABLE) == TRUE
+  OvmfPkg/PvScsiDxe/PvScsiDxe.inf
+!endif
   MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
   MdeModulePkg/Universal/MonotonicCounterRuntimeDxe/MonotonicCounterRuntimeDxe.inf
   MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf