x86: Add missed break to TAA status sysctl

Just a typo that Coverity identified.

Coverity also identified an unused store in the same functional area (x86 TAA
stuff), but this commit does not address that issue (CID 1408334).

Reported by:	Coverity
CID:		1408328, 1408332

sys/x86/x86/cpu_machdep.c

@@ -1332,6 +1332,7 @@ sysctl_taa_state_handler(SYSCTL_HANDLER_ARGS)
 		break;
 	case TAA_NOT_PRESENT:
 		state = "TSX not present";
+		break;
 	default:
 		state = "unknown";
 	}