pinctrl: mvebu: remove common get/set functions

With every SoC always providing its own get/set callbacks, we can now
remove the generic ones, remove the obsolete base address, and always
use the provided callbacks.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>