PCI: Drop pci_device_probe() test of !pci_dev->driver

When the device core calls the .probe() callback for a device, the device
is never bound, so pci_dev->driver is always NULL.

Remove the unnecessary test of !pci_dev->driver.

Link: https://lore.kernel.org/r/20211004125935.2300113-3-u.kleine-koenig@pengutronix.de


Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>