i40e: move I40E_FLAG_FILTER_SYNC to a state bit

The I40E_FLAG_FILTER_SYNC flag is modified during run time possibly when
the RTNL lock is not held. Thus, it should not be part of pf->flags, and
instead should be using atomic bit operations in the pf->state field.

Create a __I40E_MACVLAN_SYNC_PENDING state bit, and use it instead of
the old I40E_FLAG_FILTER_SYNC flag.

This is part of a larger effort to remove the need for 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>