efi_loader: make device path to text protocol customizable

The device path to text protocol is not needed for EBBR compliance. So
let's make it a customizable option.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index 2b1ae61..f3d6773 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -21,7 +21,7 @@
 obj-y += efi_boottime.o
 obj-y += efi_console.o
 obj-y += efi_device_path.o
-obj-y += efi_device_path_to_text.o
+obj-$(CONFIG_EFI_DEVICE_PATH_TO_TEXT) += efi_device_path_to_text.o
 obj-y += efi_device_path_utilities.o
 obj-y += efi_file.o
 obj-$(CONFIG_EFI_LOADER_HII) += efi_hii.o efi_hii_config.o