device: Add a new "SPI" device type

Add support for a new "SPI" device type in the devicetree to bind a
device on the SPI bus. Allow device to provide chip select number for
the device as a parameter.

Add spi_bus_operations with operation dev_to_bus which allows SoCs to
define a translation method for converting "struct device" into a unique
SPI bus number.

BUG=chrome-os-partner:59832
BRANCH=None
TEST=Compiles successfully.

Change-Id: I86f09516d3cddd619fef23a4659c9e4eadbcf3fa
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/18340
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Tested-by: build bot (Jenkins)
diff --git a/src/include/device/device.h b/src/include/device/device.h
index 47509f7..e21384b 100644
--- a/src/include/device/device.h
+++ b/src/include/device/device.h
@@ -23,6 +23,7 @@
 struct i2c_bus_operations;
 struct smbus_bus_operations;
 struct pnp_mode_ops;
+struct spi_bus_operations;
 
 /* Chip operations */
 struct chip_operations {
@@ -64,6 +65,7 @@
 #endif
 	const struct pci_operations *ops_pci;
 	const struct i2c_bus_operations *ops_i2c_bus;
+	const struct spi_bus_operations *ops_spi_bus;
 	const struct smbus_bus_operations *ops_smbus_bus;
 	const struct pci_bus_operations * (*ops_pci_bus)(device_t dev);
 	const struct pnp_mode_ops *ops_pnp_mode;