platform/chrome: cros_ec_proto: Use EC struct for features

platform/chrome: cros_ec_proto: Use EC struct for features

The Chrome EC's features are returned through an
ec_response_get_features struct, but they are stored in an independent
array. Although the two are effectively the same at present (2 unsigned
32 bit ints), there is the possibility that they could go out of sync.
Avoid this by only using the EC struct to store the features.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Link: https://lore.kernel.org/r/20211004170716.86601-1-pmalani@chromium.org
Signed-off-by: Benson Leung <bleung@chromium.org>