jmavsim_run.sh: add -r option to set the update rate

currently jmavsim uses a default rate of 500 Hz which is too much.

Tools/jmavsim_run.sh

@@ -7,7 +7,7 @@ udp_port=14560
 extra_args=
 baudrate=921600
 device=
-while getopts ":b:d:p:q" opt; do
+while getopts ":b:d:p:qr:" opt; do
 	case $opt in
 		b)
 			baudrate=$OPTARG
@@ -21,6 +21,9 @@ while getopts ":b:d:p:q" opt; do
 		q)
 			extra_args="$extra_args -qgc"
 			;;
+		r)
+			extra_args="$extra_args -r $OPTARG"
+			;;
 		\?)
 			echo "Invalid option: -$OPTARG" >&2
 			exit 1