net/i40e/base: add function to set MAC type

Make i40e_set_mac_type() public. i40e driver requires
i40e_set_mac_type() to be public. It is required for recovery mode
handling. Without this patch recovery mode could not be detected at
probe() function.

Signed-off-by: Piotr Kwapulinski <piotr.kwapulinski@intel.com>
Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Beilei Xing <beilei.xing@intel.com>