gpio: Add Delta TN48M CPLD GPIO driver

Delta TN48M switch has an onboard Lattice CPLD that is used as a GPIO
expander.

The CPLD provides 12 pins in total on the TN48M, but on more advanced
switch models it provides up to 192 pins, so the driver is extendable
to support more switches.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Link: https://lore.kernel.org/r/20220131133049.77780-3-robert.marko@sartura.hr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>