ice: convert all ring stats to u64_stats_t

ice: convert all ring stats to u64_stats_t

After several cleanups, the ice driver is now finally ready to convert all
Tx and Rx ring stats to the u64_stats_t and proper use of the u64 stats
APIs.

The final remaining part to cleanup is the VSI stats accumulation logic in
ice_update_vsi_ring_stats().

Refactor the function and its helpers so that all stat values (and not
just pkts and bytes) use the u64_stats APIs. The
ice_fetch_u64_(tx|rx)_stats functions read the stat values using
u64_stats_read and then copy them into local ice_vsi_(tx|rx)_stats
structures. This does require making a new struct with the stat fields as
u64.

The ice_update_vsi_(tx|rx)_ring_stats functions call the fetch functions
per ring and accumulate the result into one copy of the struct. This
accumulated total is then used to update the relevant VSI fields.

Since these are relatively small, the contents are all stored on the stack
rather than allocating and freeing memory.

Once the accumulator side is updated, the helper ice_stats_read and
ice_stats_inc and other related helper functions all easily translate to
use of u64_stats_read and u64_stats_inc. This completes the refactor and
ensures that all stats accesses now make proper use of the API.

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>