drm/amdkfd: Fix permissions of hang_hws

Reading from /sys/kernel/debug/kfd/hang_hws would cause a kernel
oops because we didn't implement a read callback. Set the permission
to write-only to prevent that.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: shaoyunl  <shaoyun.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_debugfs.c

@@ -93,7 +93,7 @@ void kfd_debugfs_init(void)
 			    kfd_debugfs_hqds_by_device, &kfd_debugfs_fops);
 	debugfs_create_file("rls", S_IFREG | 0444, debugfs_root,
 			    kfd_debugfs_rls_by_device, &kfd_debugfs_fops);
-	debugfs_create_file("hang_hws", S_IFREG | 0644, debugfs_root,
+	debugfs_create_file("hang_hws", S_IFREG | 0200, debugfs_root,
 			    NULL, &kfd_debugfs_hang_hws_fops);
 }