drivers: pinctrl: Add support for cc23x0 pinctrl

Add support for pinctrl to cc23x0 SoC. Like for other TI SoCs,
a node approach is implemented (no grouping approach).

Signed-off-by: Lars Thalian Morstad <l-morstad@ti.com>
Signed-off-by: Vebjorn Myklebust <v.myklebust@ti.com>
Signed-off-by: Stoyan Bogdanov <sbogdanov@baylibre.com>
Signed-off-by: Julien Panis <jpanis@baylibre.com>