net: libwx: fix VF illegal register access

net: libwx: fix VF illegal register access

Register WX_CFG_PORT_ST is a PF restricted register. When a VF is
initialized, attempting to read this register triggers an illegal
register access, which lead to a system hang.

When the device is VF, the bus function ID can be obtained directly from
the PCI_FUNC(pdev->devfn).

Fixes: a04ea57aae37 ("net: libwx: fix device bus LAN ID")
Cc: stable@vger.kernel.org
Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Link: https://patch.msgid.link/4D1F4452D21DE107+20260429083743.88961-1-jiawenwu@trustnetic.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>