staging: comedi: addi_apci_1516: merge in addi_apci_2016 driver

The low-level hardware support code for these drivers, hwdrv_apci1516.c
and hwdrv_apci2016.c, is identical. Both of these boards are 16 channel
dio boards. The 1516 board has 8 input/8 output channels and the 2016
has 16 output channels.

To ease maintainability, merge the boardinfo and pci device information
from the addi_apci_2016 driver into the addi_apci_1516 driver and modify
the Kconfig and Makefile appropriately.

This allows deleting the addi_apci_2016.c and hwdrv_apci2016.c files.

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