i40e: fix registers dump after run ethtool adapter self test

i40e: fix registers dump after run ethtool adapter self test

Fix invalid registers dump from ethtool -d ethX after adapter self test
by ethtool -t ethY. It causes invalid data display.

The problem was caused by overwriting i40e_reg_list[].elements
which is common for ethtool self test and dump.

Fixes: 22dd9ae8afcc ("i40e: Rework register diagnostic")
Signed-off-by: Radoslaw Tyl <radoslawx.tyl@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Arpana Arland <arpanax.arland@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20230328172659.3906413-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>