The contents pointed by ssi_cables[] is never changed so explicitly

declare it as const char * instead of char *.

This change have no side impact to the code itself, and is a step
forward to WARNS=6 truss(1).

sys/dev/lmc/if_lmc.h

@@ -936,7 +936,7 @@ struct ioctl
 #define IOCTL_RESET_CNTRS	  54	/* reset event counters            */
 
 /* storage for these strings is allocated here! */
-char *ssi_cables[] =
+const char *ssi_cables[] =
   {
   "V.10/EIA423",
   "V.11/EIA530A",