If RCS is not enumerated, GuC will return invalid parameters.
Make sure we do not send RCS supported when we have not enumerated
it.

Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220303223435.2793124-2-matthew.d.roper@intel.com