accel/amdxdna: Use rcu_access_pointer for __rcu pointer

Use rcu_access_pointer for pid in struct drm_file. This fixes sparse
warning.

Fixes: be462c9 ("accel/amdxdna: Add hardware context")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Signed-off-by: Lizhi Hou <[email protected]>
Reviewed-by: Mario Limonciello <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: houlz0507

drivers/accel/amdxdna/amdxdna_pci_drv.c

@@ -61,7 +61,7 @@ static int amdxdna_drm_open(struct drm_device *ddev, struct drm_file *filp)
 		goto put_rpm;
 	}
 
-	client->pid = pid_nr(filp->pid);
+	client->pid = pid_nr(rcu_access_pointer(filp->pid));
 	client->xdna = xdna;
 
 	client->sva = iommu_sva_bind_device(xdna->ddev.dev, current->mm);