mb/google/brya: Add EC mux device to brya0

Add entries to the devicetree override for brya0 and enable the Kconfig
to ensure the Chrome OS EC Mux driver is build tested.

BUG=b:208883648
TEST=None
BRANCH=None

Change-Id: Icf841cd32587f6bd98b15747283b0d331f013532
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64007
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/mainboard/google/brya/Kconfig

@@ -21,6 +21,7 @@ config BOARD_GOOGLE_BRYA_COMMON
 	select EC_GOOGLE_CHROMEEC
 	select EC_GOOGLE_CHROMEEC_BOARDID
 	select EC_GOOGLE_CHROMEEC_ESPI
+	select EC_GOOGLE_CHROMEEC_MUX
 	select EC_GOOGLE_CHROMEEC_SKUID
 	select FW_CONFIG
 	select FW_CONFIG_SOURCE_CHROMEEC_CBI

src/mainboard/google/brya/variants/brya0/overridetree.cb

@@ -707,7 +707,24 @@ chip soc/intel/alderlake
 				use conn0 as mux_conn[0]
 				use conn1 as mux_conn[1]
 				use conn2 as mux_conn[2]
-				device pnp 0c09.0 on end
+				use ecmux0 as retimer_conn[0]
+				use ecmux1 as retimer_conn[1]
+				use ecmux2 as retimer_conn[2]
+				device pnp 0c09.0 on
+					chip ec/google/chromeec/mux
+						device generic 0 on
+							chip ec/google/chromeec/mux/conn
+								device generic 0 alias ecmux0 on end
+							end
+							chip ec/google/chromeec/mux/conn
+								device generic 1 alias ecmux1 on end
+							end
+							chip ec/google/chromeec/mux/conn
+								device generic 2 alias ecmux2 on end
+							end
+						end
+					end
+				end
 			end
 		end
 		device ref pmc hidden