floppy: Do not probe number of cylinders in drive signal test

The probe test:
1. Isn't a signal test
2. Bangs the head on a 48-tpi drive
3. Doesn't actually find the true cylinder range as it
   never steps beyond cylinder 79

Thus the probe is fairly pointless and best to simply remove it.

Refs #76

testkit/floppy.c

@@ -310,13 +310,8 @@ static unsigned int drive_signal_test(unsigned int drv, struct char_row *r)
         drive_wait_ready();
 
         seek_cyl0();
-        if (cur_cyl == 0) {
-            unsigned int nr_cyls;
-            seek_track(159);
-            nr_cyls = seek_cyl0() + 1;
-            if (cur_cyl == 0)
-                sprintf(s, "-- DF%u: %u cylinders --", drv, nr_cyls);
-        }
+        if (cur_cyl == 0)
+            sprintf(s, "-- DF%u: %u cylinders --", drv, drive_param.nr_cyls);
         if (cur_cyl < 0)
             sprintf(s, "-- DF%u: No Track 0 (Drive not present?) --", drv);
         print_line(r);