cros_ec: Support reading EC features

The EC can support a variety of features and provides a way to find out
what is available. Add support for this.

Also update the feature list to the lastest available while we are here.
This is at:

   https://chromium.googlesource.com/chromiumos/platform/ec/+/refs/heads/master/include/ec_commands.h



Signed-off-by: Simon Glass <sjg@chromium.org>