efi_loader: Add GOP support

The EFI standard defines a simple boot protocol that an EFI payload can use
to access video output.

This patch adds support to expose exactly that one (and the mode already in
use) as possible graphical configuration to an EFI payload.

With this, I can successfully run grub2 with graphical output.

Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/cmd/bootefi.c b/cmd/bootefi.c
index 2f0b90a..3add632 100644
--- a/cmd/bootefi.c
+++ b/cmd/bootefi.c
@@ -141,6 +141,9 @@
 #ifdef CONFIG_PARTITIONS
 	efi_disk_register();
 #endif
+#ifdef CONFIG_LCD
+	efi_gop_register();
+#endif
 
 	/* Call our payload! */
 #ifdef DEBUG_EFI