Currently the VF can be enabled only through sysfs interface
after module loaded, but this also needs to be done when the
module loaded in some scenarios.

This patch adds module param vfs_num, adds hisi_zip_sriov_enable()
in probe, and also adjusts the position of probe.
Signed-off-by: Hao Fang <fanghao11@huawei.com>
Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>