bnx2x: constify static inline stub for dev_addr

bnx2x_vfpf_config_mac() was constified by not its stub.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>