i40e: remove FDIR_REQUIRES_REINIT driver flag

This flag hasn't been used since commit 1e1be8f6 ("i40e: ATR policy
change to flush the table to clean stale ATR rules").

Lets simplify things and just remove it.

Change-ID: I76279d84db8a2fd96f445b96aa413059f9256879
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>