staging: comedi: dt3000: use comedi_fc helpers to validate timer args

staging: comedi: dt3000: use comedi_fc helpers to validate timer args

Use the comedi_fc helper, cfc_check_trigger_arg_is(), to validate the
cmd->scan_begin_arg for the scan_begin_src TRIG_TIMER. Pass the local
variable to dt2k_ns_to_timer() instead of the cmd argument. This value
is modified by that function to return the actual time (in nanoseconds)
that the timer will be programmed with based on the calculated divisor.
The cfc_check_trigger_arg_is() helper will then validate that the
cmd->cscan_begin_arg is that value and modify it if not.

Also use cfc_check_trigger_arg_is() to validate the cmd->convert_arg
using the same logic.

Use cfc_check_trigger_arg_min() to do validate the cmd->scan_begin_arg
when the convert_src and scan_begin_src are both TRIG_TIMER.

All the arguments are unsigned int, change the local variable to an
unsigned int and rename it for aesthetic reasons.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>