tpm2-setup: terminate the option array

Otherwise bad things happen:

$ build/systemd-tpm2-setup --foo
Segmentation fault (core dumped)

src/tpm2-setup/tpm2-setup.c

@@ -63,6 +63,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "version",     no_argument,       NULL, ARG_VERSION     },
                 { "tpm2-device", required_argument, NULL, ARG_TPM2_DEVICE },
                 { "early",       required_argument, NULL, ARG_EARLY       },
+                {}
         };
 
         int c, r;