spi: spi-amd: Add AMD SPI controller driver support

This driver supports SPI Controller for AMD SOCs.This driver
supports SPI operations using FIFO mode of transfer.

Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/1587844788-33997-1-git-send-email-sanju.mehta@amd.com


Signed-off-by: Mark Brown <broonie@kernel.org>