LinuxKPI: return an address string in pci_name()

amdgpu's virtual display feature uses pci_name() to match a module parameter
string, and the documentation shows an example of `0000:26:00.0` for the name.
In our case the name was just `drmn`, which is not actually unique across
devices.

The other consumers are wireless drivers, which will benefit from this
change.

Generate the expected string for pci_name() to return.

Related to:	freebsd/drm-kmod#134
Sponsored by:	https://www.patreon.com/valpackett
Reviewed by:	bz, hselasky, manu (earlier)
MFC after:	3 days
Differential Revision: https://reviews.freebsd.org/D34248

sys/compat/linuxkpi/common/include/linux/pci.h

@@ -334,6 +334,7 @@ struct pci_dev {
 	phys_addr_t		rom;
 	size_t			romlen;
 	struct msi_desc		**msi_desc;
+	char			*path_name;
 
 	TAILQ_HEAD(, pci_mmio_region)	mmio;
 };
@@ -454,8 +455,7 @@ pci_resource_flags(struct pci_dev *pdev, int bar)
 static inline const char *
 pci_name(struct pci_dev *d)
 {
-
-	return device_get_desc(d->dev.bsddev);
+	return d->path_name;
 }
 
 static inline void *

sys/compat/linuxkpi/common/src/linux_pci.c

@@ -307,6 +307,9 @@ lkpifill_pci_dev(device_t dev, struct pci_dev *pdev)
 	pdev->subsystem_device = pci_get_subdevice(dev);
 	pdev->class = pci_get_class(dev);
 	pdev->revision = pci_get_revid(dev);
+	pdev->path_name = kasprintf(GFP_KERNEL, "%04d:%02d:%02d.%d",
+	    pci_get_domain(dev), pci_get_bus(dev), pci_get_slot(dev),
+	    pci_get_function(dev));
 	pdev->bus = malloc(sizeof(*pdev->bus), M_DEVBUF, M_WAITOK | M_ZERO);
 	/*
 	 * This should be the upstream bridge; pci_upstream_bridge()
@@ -350,6 +353,7 @@ lkpinew_pci_dev_release(struct device *dev)
 			free(pdev->msi_desc[i], M_DEVBUF);
 		free(pdev->msi_desc, M_DEVBUF);
 	}
+	kfree(pdev->path_name);
 	free(pdev, M_DEVBUF);
 }