efi_loader: use %pUs for printing GUIDs

For printing GUIDs with macro EFI_ENTRY use %pUs instead of %pUl to provide
readable debug output.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
index 6e3ee3c..3243e2c 100644
--- a/lib/efi_loader/efi_signature.c
+++ b/lib/efi_loader/efi_signature.c
@@ -174,7 +174,7 @@
 	for (siglist = db; siglist; siglist = siglist->next) {
 		/* TODO: support other hash algorithms */
 		if (guidcmp(&siglist->sig_type, &efi_guid_sha256)) {
-			EFI_PRINT("Digest algorithm is not supported: %pUl\n",
+			EFI_PRINT("Digest algorithm is not supported: %pUs\n",
 				  &siglist->sig_type);
 			break;
 		}