ice: Implement getting and setting ethtool coalesce

This patch includes the following ethtool operations:

1. get_coalesce
2. set_coalesce
3. get_per_q_coalesce
4. set_per_q_coalesce

Each ITR value (current_itr/target_itr) are stored on a per
ice_ring_container basis. This is because each valid ice_ring_container
can have 1 or more rings that are tied to the same q_vector ITR index.

Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>