spi: Add driver for Cadence SPI controller

Add driver for Cadence SPI controller. This is used in Xilinx Zynq.

Signed-off-by: Harini Katakam <harinik@xilinx.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

diff --cc drivers/spi/Kconfig
Simple merge

diff --cc drivers/spi/Makefile
Simple merge

diff --cc drivers/spi/spi-cadence.c
Simple merge