efi_loader: Add disk interfaces

A EFI applications usually want to access storage devices to load data from.

This patch adds support for EFI disk interfaces. It loops through all block
storage interfaces known to U-Boot and creates an EFI object for each existing
one. EFI applications can then through these objects call U-Boot's read and
write functions.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
[trini: Update for various DM changes since posting]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/efi_loader.h b/include/efi_loader.h
index 8b3aadd..be3c28a 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -87,6 +87,8 @@
 /* This list contains all UEFI objects we know of */
 extern struct list_head efi_obj_list;
 
+/* Called by bootefi to make all disk storage accessible as EFI objects */
+int efi_disk_register(void);
 /*
  * Stub implementation for a protocol opener that just returns the handle as
  * interface