pinctrl: imx: Split imx_pinctrl_probe() into common and mmio parts

pinctrl: imx: Split imx_pinctrl_probe() into common and mmio parts

Split imx_pinctrl_probe() into imx_pinctrl_probe_common() and
imx_pinctrl_probe_mmio(). The former does the common setup, the
later does the common setup and MMIO access configuration. The
common setup can be used as-is for SCU based systems, update
the pinctrl-imx8 to call only the common setup, update all the
other pinctrl drivers to call imx_pinctrl_probe_mmio().

No functional change.

Signed-off-by: Marek Vasut <marex@denx.de>