e1000e: provide family-specific functions to manage VLAN filter arrays

The two MAC-families that have VLAN filter table register arrays manage
each a bit differently from one another, so provide family-specific
functions for managing the register arrays and function pointers to access
the appropriate function.  Also make sure attempts to access these
register arrays are not done on parts not supporting that feature.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>