hv_netvsc: fix vf serial matching with pci slot info

[ Upstream commit 005479556197f80139771960dda0dfdcd2d2aad5 ]

The VF device's serial number is saved as a string in PCI slot's
kobj name, not the slot->number. This patch corrects the netvsc
driver, so the VF device can be successfully paired with synthetic
NIC.

Fixes: 00d7ddba ("hv_netvsc: pair VF based on serial number")
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>