gpio: 104-dio-48e: Add support for GPIO names

This patch sets the gpio_chip names option with an array of GPIO line
names that match the manual documentation for the ACCES 104-DIO-48E.
This should make it easier for users to identify which GPIO line
corresponds to a respective GPIO pin on the device.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>