spi: Add AD-FMCOMMS1-EBZ I2C-SPI bridge driver

This patch adds support for the I2C-SPI bridge which can be found on the Analog
Devices AD-FMCOMMS1-EBZ board.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>