staging: hv: re-order the code in netvsc_probe()

Re-order the code in netvsc_probe() to prevent a guest crash caused by
packets possibly received from NetVSP before call to register_netdev().

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>