staging: comedi: hwdrv_apci1564: remove magic numbers in apci1564_counter_insn_read()

Use the bit defines from addi_tcw.h to remove the magic numbers in this
function.

Add the missing define for ADDI_TCW_STATUS_HARDWARE_TRIG.

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>