dts: arm: cypress: Introduce PSoC-6 pinctrl

Introduce PSoC-6 pinctrl infraestructure and definitions.  This add
files to handle devicetree entries and following modifications:

 - add pinctrl bindings
 - update gpio bindings with pin-cells
 - add pinctrl node and move gpio nodes inside
 - declare pinctrl for current uart entries

Signed-off-by: Gerson Fernando Budke <gerson.budke@atl-electronics.com>