USB: usbtmc: fix switch statment

Steve Holland pointed out that we forgot to call break; in the switch
statment.  This probably resolves a lot of the bug reports I've gotten
for the driver lately.

Stupid me...
Reported-by: NSteve Holland <sdh4@iastate.edu>
Cc: stable <stable@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/class/usbtmc.c

@@ -927,21 +927,27 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	switch (cmd) {
 	case USBTMC_IOCTL_CLEAR_OUT_HALT:
 		retval = usbtmc_ioctl_clear_out_halt(data);
+		break;
 
 	case USBTMC_IOCTL_CLEAR_IN_HALT:
 		retval = usbtmc_ioctl_clear_in_halt(data);
+		break;
 
 	case USBTMC_IOCTL_INDICATOR_PULSE:
 		retval = usbtmc_ioctl_indicator_pulse(data);
+		break;
 
 	case USBTMC_IOCTL_CLEAR:
 		retval = usbtmc_ioctl_clear(data);
+		break;
 
 	case USBTMC_IOCTL_ABORT_BULK_OUT:
 		retval = usbtmc_ioctl_abort_bulk_out(data);
+		break;
 
 	case USBTMC_IOCTL_ABORT_BULK_IN:
 		retval = usbtmc_ioctl_abort_bulk_in(data);
+		break;
 	}
 
 	mutex_unlock(&data->io_mutex);