sim: info: convert verbose field to a bool

The verbose argument has always been an int treated as a bool, so
convert it to an explicit bool.  Further, update the API docs to
match the reality that the verbose value is actually used by some
of the internal modules.

sim/rx/gdb-if.c

@@ -644,7 +644,7 @@ sim_store_register (SIM_DESC sd, int regno, const void *buf, int length)
 }
 
 void
-sim_info (SIM_DESC sd, int verbose)
+sim_info (SIM_DESC sd, bool verbose)
 {
   check_desc (sd);