spi: Add driver for Marvell Armada 3700 SoC

spi: Add driver for Marvell Armada 3700 SoC

The SPI IP core in the Marvell Armada 3700 is similar to the one in the
other Armada SoCs. But the differences are big enough that it makes
sense to introduce a new driver instead of cluttering the old
kirkwood driver with #ifdef's.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Nadav Haklai <nadavh@marvell.com>
Cc: Kostya Porotchkin <kostap@marvell.com>
Cc: Wilson Ding <dingwei@marvell.com>
Cc: Victor Gu <xigu@marvell.com>
Cc: Hua Jing <jinghua@marvell.com>
Cc: Terry Zhou <bjzhou@marvell.com>
Cc: Hanna Hawa <hannah@marvell.com>
Cc: Haim Boot <hayim@marvell.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>