mfd: cros_ec: Separate charge-control probing from USB-PD

The charge-control subsystem in the ChromeOS EC is not strictly tied to
its USB-PD subsystem.

Since commit 7613bc0d ("mfd: cros_ec: Don't load charger with UCSI")
the presence of EC_FEATURE_UCSI_PPM would inhibit the probing of the
charge-control driver.

Furthermore recent versions of the EC firmware in Framework laptops
hard-disable EC_FEATURE_USB_PD to avoid probing cros-usbpd-charger,
which then also breaks cros-charge-control.

Instead use the dedicated EC_FEATURE_CHARGER.

Cc: stable@vger.kernel.org
Link: https://github.com/FrameworkComputer/EmbeddedController/commit/1d7bcf1d50137c8c01969eb65880bc83e424597e


Fixes: 555b5fcd ("mfd: cros_ec: Register charge control subdevice")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Tested-by: Tom Vincent <linux@tlvince.com>
Link: https://lore.kernel.org/r/20250521-cros-ec-mfd-chctl-probe-v1-1-6ebfe3a6efa7@weissschuh.net


Signed-off-by: Lee Jones <lee@kernel.org>