ec/google: Isolate EC bus protocol implementation.

The Chrome EC can be connected by different types of bus like LPC / I2C / SPI,
and the current implementation is only for LPC.

To support other types, we must first isolate the LPC protocol stuff and add
configuration variable (EC_GOOGLE_CHROMEEC_LPC) to specify bus type.

Verified by building google/link (with chromeec) configuration successfully.

Change-Id: Ib2920d8d935bcc77a5394e818f69e9265e26e8a0
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: http://review.coreboot.org/3068
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>
diff --git a/src/ec/google/chromeec/Kconfig b/src/ec/google/chromeec/Kconfig
index b8d3444..ce96da7 100644
--- a/src/ec/google/chromeec/Kconfig
+++ b/src/ec/google/chromeec/Kconfig
@@ -9,3 +9,10 @@
        default "/usr/include"
        help
          Path to the ec API file (ec/ec_commands.h).
+
+config EC_GOOGLE_CHROMEEC_LPC
+        depends on EC_GOOGLE_CHROMEEC
+	bool
+	default y if ARCH_X86
+	help
+	  Google Chrome EC via LPC bus.