ice: document RDMA devlink parameters

Commit e523af4e

 ("net/ice: Add support for enable_iwarp and enable_roce
devlink param") added support for the enable_roce and enable_iwarp
parameters in the ice driver. It didn't document these parameters in the
ice devlink documentation file. Add this documentation, including a note
about the mutual exclusion between the two modes.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Acked-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20230414162614.571861-1-jacob.e.keller@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>