ktr: Make debug.ktr.verbose available whenever KTR is configured

This is more useful and matches the documentation.  While here, make it
settable as a tunable and add a sysctl description.

PR:		139425
MFC after:	2 weeks

sys/kern/kern_ktr.c

@@ -251,9 +251,12 @@ SYSCTL_PROC(_debug_ktr, OID_AUTO, entries,
 
 #ifdef KTR_VERBOSE
 int	ktr_verbose = KTR_VERBOSE;
-TUNABLE_INT("debug.ktr.verbose", &ktr_verbose);
-SYSCTL_INT(_debug_ktr, OID_AUTO, verbose, CTLFLAG_RW, &ktr_verbose, 0, "");
+#else
+int	ktr_verbose = 0;
 #endif
+TUNABLE_INT("debug.ktr.verbose", &ktr_verbose);
+SYSCTL_INT(_debug_ktr, OID_AUTO, verbose, CTLFLAG_RWTUN, &ktr_verbose, 0,
+    "Print extra info when logging to the console");
 
 #ifdef KTR_ALQ
 struct alq *ktr_alq;
@@ -375,7 +378,6 @@ ktr_tracepoint(uint64_t mask, const char *file, int line, const char *format,
 			file += 3;
 	entry->ktr_file = file;
 	entry->ktr_line = line;
-#ifdef KTR_VERBOSE
 	if (ktr_verbose) {
 #ifdef SMP
 		printf("cpu%d ", cpu);
@@ -387,7 +389,6 @@ ktr_tracepoint(uint64_t mask, const char *file, int line, const char *format,
 		printf(format, arg1, arg2, arg3, arg4, arg5, arg6);
 		printf("\n");
 	}
-#endif
 	entry->ktr_desc = format;
 	entry->ktr_parms[0] = arg1;
 	entry->ktr_parms[1] = arg2;