siemens/mc_apl1: Enable I2C0 with 100kHz

The default setting for I2Cx is 400kHz. On this mainboard there is a
device on I2C0 which requires a lower clock rate to work correctly. For
this reason we set the frequency to 100kHz.

Change-Id: I637a58a0c89ead55ca1176d6aecdfaba5897d64f
Signed-off-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Reviewed-on: https://review.coreboot.org/22140
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/mainboard/siemens/mc_apl1/devicetree.cb

@@ -43,6 +43,11 @@ chip soc/intel/apollolake
 	# [6:0] steps of delay for HS200, each 125ps.
 	register "emmc_rx_cmd_data_cntl2" = "0x10008"
 
+	# Enable I2C0 for proximity sensor at 100kHz
+	register "i2c[0]" = "{
+		.speed = I2C_SPEED_STANDARD
+	}"
+
 	device domain 0 on
 		device pci 00.0 on  end	# - Host Bridge
 		device pci 00.1 off end	# - DPTF