efi: Move FDT-filename discovery into lib/efi

Move efi_get_distro_fdt_name() into lib/efi so it can be used from the
app.

Series-to: u-boot
Series-cc: heinrich
Cover-letter:
efi: Move some efi-loader code into a new shared dir
Some functions provided in lib/efi_loader are actually useful for the
app as well. This series refactors the Kconfig and directories a little
so that code is easier to share.

As a starting point, it moves some filename and device-path functions to
the new directory.

The next step would be to move device-path code over, but this will need
some discussion.
END

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

include/efi_device_path.h

@@ -12,7 +12,6 @@
 
 struct blk_desc;
 struct efi_load_option;
-struct udevice;
 
 /*
  * EFI_DP_END - Template end node for EFI device paths.
@@ -409,7 +408,7 @@ struct efi_device_path *search_gpt_dp_node(struct efi_device_path *device_path);
  *
  * Set the device path to an IPv4 path as provided by efi_dp_from_ipv4
  * concatenated with a device path of subtype DEVICE_PATH_SUB_TYPE_MSG_URI,
- * and an EFI_DP_END node.
+ * and an EFI_DP_3 node.
  *
  * @server:	URI of remote server
  * @dev:	net udevice