ec/google/chromeec: Add config option for eSPI

The Intel platforms using eSPI EC communication have just been enabling
the EC_GOOGLE_CHROMEEC_LPC option for simplicity.  This does basically
the same, but at least marks it as eSPI in Kconfig for clarity.

BUG=b:140055300
TEST=Build tested only.

Change-Id: Ib56ec9d1dc204809a05c846494ff0e0d69cf70ea
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35128
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Mathew King <mathewk@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/ec/google/chromeec/Kconfig b/src/ec/google/chromeec/Kconfig
index 3eb2c48..2242653 100644
--- a/src/ec/google/chromeec/Kconfig
+++ b/src/ec/google/chromeec/Kconfig
@@ -47,6 +47,17 @@
 	help
 	  Use only proto3 for i2c EC communication.
 
+config EC_GOOGLE_CHROMEEC_ESPI
+	depends on EC_GOOGLE_CHROMEEC && ARCH_X86  # Needs Plug-and-play.
+	def_bool n
+	select EC_GOOGLE_CHROMEEC_LPC
+	help
+	  Google Chrome EC via eSPI bus.
+
+	  The EC communication code is the same between eSPI and LPC, so
+	  this option simply enables the LPC EC code.  The eSPI device
+	  still needs to correctly configure the bus transactions.
+
 config EC_GOOGLE_CHROMEEC_LPC
 	depends on EC_GOOGLE_CHROMEEC && ARCH_X86  # Needs Plug-and-play.
 	def_bool y