ixgbe: add the ability for the PF to disable VF link state

ixgbe: add the ability for the PF to disable VF link state

Add support for ndo_set_vf_link_state the Network Device Option that
allows the PF driver to control the virtual link state of the VF devices.
Without this change a VF cannot be disabled/enabled by the administrator.
In the implementation the auto state takes over PF link state to
VF link setting, the enable state is not supported, the disable state
shut off the VF link regardless of the PF setting.

Signed-off-by: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>