pinctrl: mvebu: pinctrl driver core

This patch adds a pinctrl driver core for Marvell SoCs plus DT
binding documentation. This core driver will be used by SoC family
specific drivers, i.e. Armada XP, Armada 370, Dove, Kirkwood, aso.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>
Conflicts:

	arch/arm/Kconfig