ARM: mvebu: adjust Armada XP DT spi muxing after pinctrl function rename

Following the merge of "pinctrl: mvebu: armada-xp: rename spi to spi0"
by Linus Walleij, we need to adjust the Armada XP Device Tree
accordingly, by adjusting the pinctrl configuration for SPI pins.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>