siemens/mc_bdx1: Enable PCA9538 I/O expander

The I/O expander on the mc_bdx1 is used to get the hardware version of
the mainboard. This patch enables the chip driver for the I/O expander.

Change-Id: I98c667fe4dccf0698ab4cb5ede6082f020c70ec6
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/23749
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/mainboard/siemens/mc_bdx1/Kconfig

@@ -13,6 +13,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select DRIVER_INTEL_I210
 	select DRIVER_SIEMENS_NC_FPGA
 	select DRIVERS_I2C_RX6110SA
+	select DRIVERS_I2C_PCA9538
 
 config MAINBOARD_DIR
 	string

src/mainboard/siemens/mc_bdx1/devicetree.cb

@@ -23,6 +23,13 @@ chip soc/intel/fsp_broadwell_de
 				register "user_weekday" = "4"
 				device i2c 0x32 on end	# RTC RX6110 SA
 			end
+			#Enable I/O expander
+			chip drivers/i2c/pca9538
+				register "in_out" = "0xff"
+				register "invert" = "0x00"
+				register "out_val" = "0x00"
+				device i2c 0x71 on end # I/O expander
+			end
 		end # SMBus Controller
 		device pci 1f.5 on end # SATA Controller
 	end