netdevsim: fix uninit value in nsim_drv_configure_vfs()

Build bot points out that I missed initializing ret
after refactoring.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 1c401078 ("netdevsim: move details of vf config to dev")
Link: https://lore.kernel.org/r/20211101221845.3188490-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>