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.