i40e: Use proper enum in i40e_ndo_set_vf_link_state

Clang warns when one enumerated type is converted implicitly to another.

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c:4214:42: warning:
implicit conversion from enumeration type 'enum i40e_aq_link_speed' to
different enumeration type 'enum virtchnl_link_speed'
      [-Wenum-conversion]
                pfe.event_data.link_event.link_speed = I40E_LINK_SPEED_40GB;
                                                     ~ ^~~~~~~~~~~~~~~~~~~~
1 warning generated.

Use the proper enum from virtchnl_link_speed, which has the same value
as I40E_LINK_SPEED_40GB, VIRTCHNL_LINK_SPEED_40GB. This appears to be
missed by commit ff3f4cc2 ("virtchnl: finish conversion to virtchnl
interface").

Link: https://github.com/ClangBuiltLinux/linux/issues/81


Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>