JTAG: Amontec JTAG accelerater "rtck" is back

The command processing conversion a while back lost the
"rtck" enable/disable command; restore it.

NOTE that having such a command is wrong; there's a standard
way to enable adaptive clocking ("speed 0").

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

src/jtag/drivers/amt_jtagaccel.c

@@ -577,7 +577,7 @@ static const struct command_registration amtjtagaccel_command_handlers[] = {
 		.usage = "<port_num>",
 	},
 	{
-		.name = "parport_port",
+		.name = "rtck",
 		.handler = &amt_jtagaccel_handle_rtck_command,
 		.mode = COMMAND_CONFIG,
 		.help = "enable RTCK",