The initial mxs pinctrl support, commit 17723111 (pinctrl: add
pinctrl-mxs support) skipped creating group from device tree pin config
node.  Add it to get pin config node work for client device.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>