drm/nouveau/pci: Move a variable assignment behind condition checks in nvkm_pcie_set_link()

The address of a data structure member was determined before
a corresponding null pointer check in the implementation of
the function “nvkm_pcie_set_link”.

Thus avoid the risk for undefined behaviour by moving the assignment
for the variable “subdev” behind some condition checks.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b31019b1-bb73-ed93-3378-e551e17a4f32@web.de

drivers/gpu/drm/nouveau/nvkm/subdev/pci/pcie.c

@@ -114,7 +114,7 @@ nvkm_pcie_init(struct nvkm_pci *pci)
 int
 nvkm_pcie_set_link(struct nvkm_pci *pci, enum nvkm_pcie_speed speed, u8 width)
 {
-	struct nvkm_subdev *subdev = &pci->subdev;
+	struct nvkm_subdev *subdev;
 	enum nvkm_pcie_speed cur_speed, max_speed;
 	struct pci_bus *pbus;
 	int ret;
@@ -126,6 +126,7 @@ nvkm_pcie_set_link(struct nvkm_pci *pci, enum nvkm_pcie_speed speed, u8 width)
 	if (!pci->func->pcie.set_link)
 		return -ENOSYS;
 
+	subdev = &pci->subdev;
 	nvkm_trace(subdev, "requested %s\n", nvkm_pcie_speeds[speed]);
 
 	if (pci->func->pcie.version(pci) < 2) {