net/i40e/base: skip further adminq init for VF

Since VF has no need of firmware, we can skip further adminq init which
involves firmware operation, this patch fixes the testpmd segfault issue
when starting with i40e VF.

Fixes: d5e1a149362e ("net/i40e/base: check MAC type")

Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
Acked-by: Beilei Xing <beilei.xing@intel.com>