UPSTREAM: pinmux: hsdk: Convert ARC HSDK pinmux to be devicetree based

Add a simple pinctrl node for the CREG GPIO MUX register to be used
by the pinmux driver.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
(cherry picked from commit 4276d7d2471a1a38f7e558334a86aed6a9c4a6fd)

TEST=none
BUG=none

Change-Id: I38b14b703a40e605e5dedcc70ecf35d80dfe07d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/2876314
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Denis Brockus <dbrockus@chromium.org>
Tested-by: Denis Brockus <dbrockus@chromium.org>
Commit-Queue: Denis Brockus <dbrockus@chromium.org>
6 files changed