ChromeOS: Drop filling ECFW_RW/RO state in CNVS

This field was never meant to be filled out by coreboot, because it
can't know what the right value for this will be by the time the OS
is running, so anything coreboot could fill in here is premature.

This field is only read by the chromeos-specific `crossystem` utility,
not by kernel code, so if one does not run through depthcharge there'll
be many more broken assumptions in CNVS anyway.

Change-Id: Ia56b3a3fc82f1b8247a6ee512fe960e9d3d87585
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63290
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/mainboard/google/butterfly/chromeos.c

@@ -48,15 +48,6 @@ int get_recovery_mode_switch(void)
 	return 0;
 }
 
-bool mainboard_ec_running_ro(void)
-{
-	// TODO: MLR
-	// The firmware read/write status is a "virtual" switch and
-	// will be handled elsewhere.  Until then hard-code to
-	// read/write instead of read-only for developer mode.
-	return false;
-}
-
 static const struct cros_gpio cros_gpios[] = {
 	CROS_GPIO_REC_AH(CROS_GPIO_VIRTUAL, CROS_GPIO_DEVICE_NAME),
 	CROS_GPIO_WP_AL(WP_GPIO, CROS_GPIO_DEVICE_NAME),