staging: comedi: Check length of INSN_CONFIG_TIMER_1 instruction

The contents of the Comedi configuration instruction
`INSN_CONFIG_TIMER_1` instruction are not very well defined, but the one
driver that uses it (the "cb_pcidas64" driver for the PCI-DAS4020/12
card) assumes its `insn->n` is 5. Add a check in
`check_insn_config_length()` to verify that `insn->n` is correct for
this configuration instruction.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -1209,6 +1209,7 @@ static int check_insn_config_length(struct comedi_insn *insn,
 		break;
 	case INSN_CONFIG_PWM_OUTPUT:
 	case INSN_CONFIG_ANALOG_TRIG:
+	case INSN_CONFIG_TIMER_1:
 		if (insn->n == 5)
 			return 0;
 		break;