pinctrl: mxs: Add support for i.MX2[38] mxs pinctrl driver

The code responsible for setting proper values in the MUX registers
(in the mxs_pinctrl_set_state()) has been ported from Linux kernel
- SHA1: 17bb763e7eaf tag v5.1.11 from linux-stable.

As the pinctrl node in the imx28.dtsi file has gpio pins nodes as subnodes,
it was necessary to use 'dm_scan_fdt_dev()' (as a .bind method) to also
make them 'visible' by the DM's "gpio_mxs" driver.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Marek Vasut <marex@denx.de>
diff --git a/drivers/pinctrl/nxp/Makefile b/drivers/pinctrl/nxp/Makefile
index b340d94..b86448a 100644
--- a/drivers/pinctrl/nxp/Makefile
+++ b/drivers/pinctrl/nxp/Makefile
@@ -6,4 +6,5 @@
 obj-$(CONFIG_PINCTRL_IMX_SCU)		+= pinctrl-scu.o
 obj-$(CONFIG_PINCTRL_IMX8)		+= pinctrl-imx8.o
 obj-$(CONFIG_PINCTRL_IMX8M)		+= pinctrl-imx8m.o
+obj-$(CONFIG_PINCTRL_MXS)		+= pinctrl-mxs.o
 obj-$(CONFIG_PINCTRL_VYBRID)		+= pinctrl-vf610.o