gpio: 104-idi-48: Implement and utilize register structures

gpio: 104-idi-48: Implement and utilize register structures

Reduce magic numbers and improve code readability by implementing and
utilizing named register data structures. The 104-IDI-48 device features
an Intel 8255 compatible GPIO interface, so the i8255 GPIO module is
selected and utilized as well.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: John Hentges <jhentges@accesio.com>
Cc: Jay Dolan <jay.dolan@accesio.com>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>