arm: mvebu: define and use common Armada XP SPI pinctrl setting

arm: mvebu: define and use common Armada XP SPI pinctrl setting

This patch defines common Armada XP pinctrl settings in armada-xp.dtsi
for the supported SPI interface (MPP36-39) and use it as default
for Armada XP spi interface. That being done, it removes the now
redundant definitions in armada-xp-axpwifiap.dts.

Note: this patch has the potential to break out-of-tree users w/o
specific pinctrl settings for their spi interfaces if the default
above does not match their config (i.e. if they do not use CS0).

Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Link: https://lkml.kernel.org/r/d404b7abd80ee5a0fd8e8d3586d33cd37740d589.1416613429.git.arno@natisbad.org
Signed-off-by: Jason Cooper <jason@lakedaemon.net>