platform/chrome: cros_ec_proto: Use ec_command for check_features

Use the existing cros_ec_command() for cros_ec_check_features(). This
eliminates an unnecessary duplication of the memory allocation/free and
memory copy code.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Link: https://lore.kernel.org/r/20211004170716.86601-2-pmalani@chromium.org


Signed-off-by: Benson Leung <bleung@chromium.org>