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/Kconfig b/drivers/pinctrl/nxp/Kconfig
index 61f93be..f2e67ca 100644
--- a/drivers/pinctrl/nxp/Kconfig
+++ b/drivers/pinctrl/nxp/Kconfig
@@ -89,6 +89,16 @@
 	  only parses the 'fsl,pins' property and configure related
 	  registers.
 
+config PINCTRL_MXS
+	bool "NXP MXS pinctrl driver"
+	depends on ARCH_MX28 && PINCTRL_FULL
+	help
+	  Say Y here to enable the i.MX mxs pinctrl driver
+
+	  This option provides a simple pinctrl driver for i.MX mxs SoC
+	  familiy, e.g. i.MX28. This feature depends on device tree
+	  configuration.
+
 config PINCTRL_VYBRID
 	bool "Vybrid (vf610) pinctrl driver"
 	depends on ARCH_VF610 && PINCTRL_FULL