platform/chrome: Move cros-ec transport drivers to drivers/platform.

There are some cros-ec transport drivers (I2C, SPI) living in MFD, while
others (LPC) living in drivers/platform. The transport drivers are more
platform specific. So, move the I2C and SPI transport drivers to the
platform/chrome directory. The patch also removes the MFD_ prefix of
their Kconfig symbols.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Benson Leung <bleung@chromium.org>

drivers/platform/chrome/Kconfig

@@ -52,6 +52,26 @@ config CHROMEOS_TBMC
 config CROS_EC_CTL
         tristate
 
+config CROS_EC_I2C
+	tristate "ChromeOS Embedded Controller (I2C)"
+	depends on MFD_CROS_EC && I2C
+
+	help
+	  If you say Y here, you get support for talking to the ChromeOS
+	  EC through an I2C bus. This uses a simple byte-level protocol with
+	  a checksum. Failing accesses will be retried three times to
+	  improve reliability.
+
+config CROS_EC_SPI
+	tristate "ChromeOS Embedded Controller (SPI)"
+	depends on MFD_CROS_EC && SPI
+
+	---help---
+	  If you say Y here, you get support for talking to the ChromeOS EC
+	  through a SPI bus, using a byte-level protocol. Since the EC's
+	  response time cannot be guaranteed, we support ignoring
+	  'pre-amble' bytes before the response actually starts.
+
 config CROS_EC_LPC
         tristate "ChromeOS Embedded Controller (LPC)"
         depends on MFD_CROS_EC && ACPI && (X86 || COMPILE_TEST)