Add some default cases for unreachable code to silence compiler warnings.

This was caused by r361481 when the buffer type was changed from an
int to an enum.

Reported by:	mjg, rpokala
Sponsored by:	Chelsio Communications

sys/mips/cavium/cryptocteon/cryptocteon.c

@@ -323,6 +323,8 @@ cryptocteon_process(device_t dev, struct cryptop *crp, int hint)
 			goto done;
 		}
 		break;
+	default:
+		break;
 	}
 
 	if (csp->csp_cipher_alg != 0) {

sys/mips/nlm/dev/sec/nlmseclib.c

@@ -157,6 +157,8 @@ nlm_crypto_form_srcdst_segs(struct xlp_sec_command *cmd,
 			    crp->crp_buf.cb_buf, crp->crp_buf.cb_buf_len);
 		}
 		break;
+	default:
+		__assert_unreachable();
 	}
 	return (0);
 }