i40e: prevent memory leak in i40e_setup_macvlans

In i40e_setup_macvlans if i40e_setup_channel fails the allocated memory
for ch should be released.

Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>