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: Steve Holland <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/class/usbtmc.c

···
 	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);