pinctrl: mvebu: armada-xp: remove non-existing NAND pins

After updating to a more recent version of the Armada XP datasheet, we
realized that some of the pins documented as having a NAND-related
functionality in fact did not have such functionality. This commit
updates the pinctrl driver accordingly.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: <stable@vger.kernel.org> # v3.7+
Fixes: 463e270f ("pinctrl: mvebu: add pinctrl driver for Armada XP")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>