pinctrl: mvebu: use correct MPP sel value for dev pins

The "dev" function is selected with the value 0x4 not 0x01.

Fixes: commit d7ae8f8d

 ("pinctrl: mvebu: pinctrl driver for 98DX3236 SoC")
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>