mb/google/brox: Enable EC SW Sync

Now that EC software sync has been verified to work on Brox, we can
enable it by default.

BUG=b:326152804
BRANCH=None
TEST=Verify that SW sync occurs

Change-Id: I3d356c006fc448125605761f7328d1f1e203a7c4
Signed-off-by: Shelley Chen <shchen@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81211
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/brox/Kconfig

@@ -66,7 +66,6 @@ config BASEBOARD_DIR
 
 config CHROMEOS
 	select EC_GOOGLE_CHROMEEC_SWITCHES
-	select GBB_FLAG_DISABLE_EC_SOFTWARE_SYNC
 	select GBB_FLAG_DISABLE_PD_SOFTWARE_SYNC
 	select HAS_RECOVERY_MRC_CACHE