efi: app: Implement %pD in the app

This printf() extension is useful for the app. Add an implementation of
efi_dp_str() so that it works as expected.

Signed-off-by: Simon Glass <sjg@chromium.org>

lib/efi/Kconfig

@@ -11,12 +11,22 @@ config EFI
 
 	  This is used to provide libraries shared by both.
 
+if EFI_LOADER
+
 config EFI_BINARY_EXEC
 	bool "Execute UEFI binary"
 	default y
-	depends on EFI_LOADER
 	help
 	  Select this option if you want to execute the UEFI binary after
 	  loading it with U-Boot load commands or other methods.
 	  You may enable CMD_BOOTEFI_BINARY so that you can use bootefi
 	  command to do that.
+
+config EFI_DEVICE_PATH_TO_TEXT
+	bool "Device path to text protocol"
+	default y
+	help
+	  The device path to text protocol converts device nodes and paths to
+	  human readable strings.
+
+endif # EFI_LOADER