netvsc: fix ptr_ret.cocci warnings

drivers/net/hyperv/netvsc_drv.c:737:8-14: WARNING: PTR_ERR_OR_ZERO can be used

 Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci

Fixes: 9749fed5 ("netvsc: use ERR_PTR to avoid dereference issues")
CC: stephen hemminger <stephen@networkplumber.org>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>