OvmfPkg/QemuBootOrderLib: add StoreQemuBootOrder()

The function reads the boot order from qemu fw_cfg, translates it into
device paths and stores them in 'QemuBootOrderNNNN' variables.  In case
there is no boot ordering configured the function will do nothing.

Use case: Allow applications loaded via 'qemu -kernel bootloader.efi'
obey the boot order.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c

@@ -1694,6 +1694,11 @@ PlatformBootManagerAfterConsole (
   //
   PciAcpiInitialization ();
 
+  //
+  // Write qemu bootorder to efi variables
+  //
+  StoreQemuBootOrder ();
+
   //
   // Process QEMU's -kernel command line option
   //