drivers/i2c/generic: Fix compile failure

This variable name was changed in chip.h but not the consumer
and it was submitted before it was caught.

Change-Id: I7c492b588b2fd854a9eeac36029a46da324a7b1b
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/15109
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/drivers/i2c/generic/generic.c

@@ -32,7 +32,7 @@ static void i2c_generic_fill_ssdt(struct device *dev)
 	struct acpi_i2c i2c = {
 		.address = dev->path.i2c.device,
 		.mode_10bit = dev->path.i2c.mode_10bit,
-		.speed = config->bus_speed ? : I2C_SPEED_FAST,
+		.speed = config->speed ? : I2C_SPEED_FAST,
 		.resource = scope,
 	};