Change grub_install_register_efi interface to pass GRUB device.

This allows grub_install_register_efi to request partition info
	directly.

include/grub/util/install.h

@@ -205,7 +205,7 @@ const char *
 grub_install_get_default_x86_platform (void);
 
 void
-grub_install_register_efi (const char *efidir_disk, int efidir_part,
+grub_install_register_efi (grub_device_t efidir_grub_dev,
 			   const char *efifile_path,
 			   const char *efi_distributor);