efi_loader: Clean up efi_dp_append and efi_dp_concat

Looking back at the initrd storing functionality, we introduced three
functions, efi_dp_append_or_concatenate(), efi_dp_append/concat(). In
hindsight we could have simplified that by a lot. First of all none of
the functions append anything. They all allocate a new device path and
concatenate the contents of two device paths in one. A boolean parameter
controls the final device path -- if that's true an end node is injected
between the two device paths.

So let's rewrite this and make it a bit easier to read. Get rid of
efi_dp_append(), efi_dp_concat() and rename
efi_dp_append_or_concatenate() to efi_dp_concat(). This is far more
intuitive and the only adjustment that is needed is an extra boolean
argument on all callsites.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
index a032d3a..dd2dd23 100644
--- a/lib/efi_loader/efi_bootmgr.c
+++ b/lib/efi_loader/efi_bootmgr.c
@@ -143,7 +143,7 @@
 		if (!dp)
 			continue;
 
-		dp = efi_dp_append(dp, fp);
+		dp = efi_dp_concat(dp, fp, false);
 		if (!dp)
 			continue;
 
@@ -1579,8 +1579,8 @@
 			goto out;
 		msg_path = file_path;
 	} else {
-		file_path = efi_dp_append(bootefi_device_path,
-					  bootefi_image_path);
+		file_path = efi_dp_concat(bootefi_device_path,
+					  bootefi_image_path, false);
 		msg_path = bootefi_image_path;
 		log_debug("Loaded from disk\n");
 	}