efi_loader: initialize return values in efi_uninstall_multiple_protocol_interfaces_int()

If the va_list we got handed over contains no protocols we must return
EFI_SUCCESS.  However in that case the current code just returns
an unintialized value.
Fix that by setting the return value in the variable definition

Addresses-Coverity: CID 376195:  ("Uninitialized variables  (UNINIT)")
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index a560215..253f9f7 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -2754,7 +2754,7 @@
 {
 	const efi_guid_t *protocol;
 	void *protocol_interface;
-	efi_status_t ret;
+	efi_status_t ret = EFI_SUCCESS;
 	size_t i = 0;
 	efi_va_list argptr_copy;