ixgbe: fix large MTU request from VF

Check that the MTU value requested by the VF is in the supported
range of MTUs before attempting to set the VF large packet enable,
otherwise reject the request. This also avoids unnecessary
register updates in the case of the 82599 controller.

Fixes: 872844dd

 ("ixgbe: Enable jumbo frames support w/ SR-IOV")
Co-developed-by: Piotr Skajewski <piotrx.skajewski@intel.com>
Signed-off-by: Piotr Skajewski <piotrx.skajewski@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Co-developed-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Signed-off-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>