staging: greybus: shape up greybus GPIO

Greybus GPIO seems to reimplement the already existing generic
gpiolib irqchip. Also use gpiochip_get_data(). Also use
devm_gpiochip_add_data().

Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Axel Haslam <haslam_axel@projectara.com>
Cc: Johan Hovold <johan@hovoldconsulting.com>
Cc: Sandeep Patil <patil_sandeep@projectara.com>
Cc: Rui Miguel Silva <rui.silva@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Rebased to v4.13.
ChangeLog v1->v2:
- Add the hunk adding select GPIOLIB_IRQCHIP to Kconfig,
  sorry for sending patches too late in the night.

Greybus folks: please look at this. I expect something like this
to be applied before migrating from staging, I can't test it
obviously.
2 files changed