torture: Add kvm.sh --help and update help message

This commit adds a --help argument (along with its synonym -h) to display
the help text.  While in the area, this commit also updates the help text.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/kvm.sh

@@ -56,17 +56,18 @@ usage () {
 	echo "       --defconfig string"
 	echo "       --dryrun sched|script"
 	echo "       --duration minutes"
+	echo "       --help"
 	echo "       --interactive"
 	echo "       --jitter N [ maxsleep (us) [ maxspin (us) ] ]"
 	echo "       --kconfig Kconfig-options"
 	echo "       --kmake-arg kernel-make-arguments"
 	echo "       --mac nn:nn:nn:nn:nn:nn"
-	echo "       --memory megabytes | nnnG"
+	echo "       --memory megabytes|nnnG"
 	echo "       --no-initrd"
 	echo "       --qemu-args qemu-arguments"
 	echo "       --qemu-cmd qemu-system-..."
 	echo "       --results absolute-pathname"
-	echo "       --torture rcu"
+	echo "       --torture lock|rcu|rcuperf|refscale|scf"
 	echo "       --trust-make"
 	exit 1
 }
@@ -127,6 +128,9 @@ do
 		dur=$(($2*60))
 		shift
 		;;
+	--help|-h)
+		usage
+		;;
 	--interactive)
 		TORTURE_QEMU_INTERACTIVE=1; export TORTURE_QEMU_INTERACTIVE
 		;;