soc/intel/skylake: move i2c voltage config to own variable

In preparation of merging the lpss i2c config structures on
apollolake and skylake move the i2c voltage variable to its
own field. It makes refactoring things easier, and then there's
no reason for a separate SoC specific i2c config structure.

BUG=chrome-os-partner:58889

Change-Id: Ibcc3cba9bac3b5779351b673bc0cc7671d127f24
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/17347
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

src/soc/intel/skylake/chip.h

@@ -40,8 +40,6 @@ enum skylake_i2c_voltage {
 };
 
 struct skylake_i2c_config {
-	/* Bus voltage level, default is 3.3V */
-	enum skylake_i2c_voltage voltage;
 	/* Bus speed in Hz, default is I2C_SPEED_FAST (400 KHz) */
 	enum i2c_speed speed;
 	/* Bus should be enabled prior to ramstage with temporary base */
@@ -201,6 +199,8 @@ struct soc_intel_skylake_config {
 	u8 SerialIoDevMode[PchSerialIoIndexMax];
 
 	/* I2C */
+	/* Bus voltage level, default is 3.3V */
+	enum skylake_i2c_voltage i2c_voltage[SKYLAKE_I2C_DEV_MAX];
 	struct skylake_i2c_config i2c[SKYLAKE_I2C_DEV_MAX];
 
 	/* Camera */