i40e: move I40E_FLAG_TEMP_LINK_POLLING to state field

This flag is modified outside of the RTNL lock and thus should not be
part of the pf->flags variable.

Use a state bit instead, so that we can use atomic bit operations.

This is part of a larger effort to remove cmpxchg64 in
i40e_set_priv_flags()

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>