ice: use u64_stats API to access pkts/bytes in dim sample

ice: use u64_stats API to access pkts/bytes in dim sample

The __ice_update_sample and __ice_get_ethtool_stats functions directly
accesses the pkts and bytes counters from the ring stats. A following
change is going to update the fields to be u64_stats_t type, and will need
to be accessed appropriately. This will ensure that the accesses do not
cause load/store tearing.

Add helper functions similar to the ones used for updating the stats
values, and use them. This ensures use of the syncp pointer on 32-bit
architectures. Once the fields are updated to u64_stats_t, it will then
properly avoid tears on all architectures.

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>