ARM: mvebu: Add a number of pinctrl functions

Some pinctrl functions can be shared with all DTS out there, since they are
generic, SoC-wide muxing options. Add a number of these to the DTSI to avoid
duplication.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>