pinctrl: mvebu: dove: use remapped mpp4 register

Now that we have an ioremapped mpp4 register, get rid of hardcoded
physical addresses. While at it, also remove DOVE_ prefix from those
macros.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>