pinctrl: pinctrl-imx: fix map setting problem if NO_PAD_CTL is set

new_map is allocated according to map_num instead of grp->npins,
if a pin or some pins of a group has NO_PAD_CTL property, the map_num
and the grp->npin are different definitely.

When we set mapping information to the new_map[], we should skip those
pins with NO_PAD_CTL from index, otherwise it is possible the driver
will aceesss to a unallocated region.

Acked-by: Dong Aisheng <dong.aisheng@linaro.org>
Cc: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Hui Wang <jason77.wang@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>