Set the read_reg_mdi and write_reg_mdi method pointers for
X550EM_A_10G_T devices to resolve jumping to NULL.
Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>