arm: mvebu: Add support for SPI controller in Armada 370/XP

The Armada 370 and Armada XP SoC has an SPI controller.
This patch adds support for this controller in Armada 370
and Armada XP SoC common device tree files.

Note that the Armada XP SPI register length is 0x50 bytes,
while Armada 370 SPI register length is 0x28 bytes,
so we choose the smaller of the two.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Lior Amsalem <alior@marvell.com>
Acked-by: Gregory Clement <gregory.clement@free-electrons.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>