gps: improvements and corrections for config commands

This contains some improvements and corrections for the gps driver
It adds some additional functions for different modes (automobile, bike, etc)
and also ignores the return results from any config commands.

Basically due to the fact that there is a constant stream of updates
coming from NMEA messages, the results from sending any UBX commands
are getting lost. Better to just ignore them for now.

Signed-off-by: deadprogram <ron@hybridgroup.com>

examples/gps/uart/main.go

@@ -52,7 +52,10 @@ func main() {
 			}
 			println()
 		} else {
-			println("Waiting for fix...")
+			if fix.Type == gps.GSV {
+				// GSV sentence provides satellite count even if no fix yet
+				println(fix.Satellites, "satellites visible")
+			}
 		}
 		time.Sleep(200 * time.Millisecond)
 	}