i40e: move I40E_FLAG_UDP_FILTER_SYNC to the state field

This flag is modified during run time, possibly even when the RTNL lock
is not held. Additionally it has a few places which should be using
test_and_set or test_and_clear atomic bit operations.

Create a new state bit __I40E_UDP_SYNC_PENDING and use it instead of the
ole I40E_FLAG_UDP_FILTER_SYNC flag.

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