staging: comedi: addi_apci_1564: don't allocate unused subdevices

The addi-data common code always allocates 7 subdevices.  This driver
cannot or will not use the ones we are currently allocating for analog
input and output or EEPROM, so just don't allocate these subdevices at
all.

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