platform/chrome: cros_ec_lpc - Depend on X86 || COMPILE_TEST

The ChromeOS EC is connected by LPC only on x86 platforms and no others,
so add a dependency describing that.

But also build the driver if the COMPILE_TEST option is enabled
to have build coverage in other architectures.
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
[olof: reworded commit message]
Signed-off-by: Olof Johansson <olof@lixom.net>

drivers/platform/chrome/Kconfig

@@ -49,7 +49,7 @@ config CROS_EC_CHARDEV
 
 config CROS_EC_LPC
         tristate "ChromeOS Embedded Controller (LPC)"
-        depends on MFD_CROS_EC
+        depends on MFD_CROS_EC && (X86 || COMPILE_TEST)
         help
           If you say Y here, you get support for talking to the ChromeOS EC
           over an LPC bus. This uses a simple byte-level protocol with a