efi: Support copy framebuffer

Add support for this to EFI in case it becomes useful. At present it just
slows things down. You can enable CONFIG_VIDEO_COPY to turn it on.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/dts/efi-x86_app.dts b/arch/x86/dts/efi-x86_app.dts
index 6d843a9..59e2e40 100644
--- a/arch/x86/dts/efi-x86_app.dts
+++ b/arch/x86/dts/efi-x86_app.dts
@@ -27,6 +27,7 @@
 	};
 	efi-fb {
 		compatible = "efi-fb";
+		bootph-some-ram;
 	};
 
 };