OvmfPkg: Add QemuFlashFvbServicesRuntimeDxe to firmware image

OvmfPkg: Add QemuFlashFvbServicesRuntimeDxe to firmware image

This driver will support a flash FVB implementation if QEMU flash
is detected.

The driver is added to the apriori list to make sure it runs
before the EmuVariableFvbRuntimeDxe driver. If this driver detects
flash support, then it will disable the EmuVariableFvbRuntimeDxe
driver by setting PcdFlashNvStorageVariableBase64.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14840 6f19259b-4bc3-4df7-8a09-765794883524