drm/amdgpu: fix the logic to validate fpriv and root bo

Fix the smatch warning,
smatch warnings:
drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c:2146 amdgpu_pt_info_read()
error: we previously assumed 'fpriv' could be null (see line 2146)

"if (!fpriv && !fpriv->vm.root.bo)", It has to be an OR condition
rather than an AND which makes an NULL dereference in case fpriv is NULL.

Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Signed-off-by: Sunil Khatri <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Christian König <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c

···
 		return -EINVAL;
 
 	fpriv = file->driver_priv;
-	if (!fpriv && !fpriv->vm.root.bo)
+	if (!fpriv || !fpriv->vm.root.bo)
 		return -ENODEV;
 
 	root_bo = amdgpu_bo_ref(fpriv->vm.root.bo);