of/unittest: fix infinite loop in of_unittest_destroy_tracked_overlays()

of_overlay_destroy() can return `-ENODEV' error code once it
failed to find the requested overlay in `ov_idr'. However,
of_unittest_destroy_tracked_overlays() does not handle this
error code correctly and continues to call of_overlay_destroy()
on the 'missing' overlay over and over again. This results in
a printk flood

[..]
[   33.497583] of_overlay_destroy: Could not find overlay #6
[   33.497583] of_overlay_destroy: Could not find overlay #6
[   33.497584] ### dt-test ### of_unittest_destroy_tracked_overlays: overlay destroy failed for #6
[   33.497584] ### dt-test ### of_unittest_destroy_tracked_overlays: overlay destroy failed for #6
[   33.497586] of_overlay_destroy: Could not find overlay #6
[   33.497586] of_overlay_destroy: Could not find overlay #6
[   33.497587] ### dt-test ### of_unittest_destroy_tracked_overlays: overlay destroy failed for #6
[   33.497587] ### dt-test ### of_unittest_destroy_tracked_overlays: overlay destroy failed for #6
[..]

which is not really good due to printk design, and can lead to soft
lockups, hard lockups, etc. (depending on the context console_unlock()
is being called from). The problem has bee observed in real life
and reported by Ying Huang.

This patch does not address the root cause of missing overlay in
`ov_idr', it fixes the endless loop only.
Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Nkernel test robot <ying.huang@linux.intel.com>
Link: lkml.kernel.org/r/87fuwk1c0o.fsf@yhuang-dev.intel.com
Signed-off-by: NRob Herring <robh@kernel.org>

drivers/of/unittest.c

@@ -1165,6 +1165,11 @@ static void of_unittest_destroy_tracked_overlays(void)
 				continue;
 
 			ret = of_overlay_destroy(id + overlay_first_id);
+			if (ret == -ENODEV) {
+				pr_warn("%s: no overlay to destroy for #%d\n",
+					__func__, id + overlay_first_id);
+				continue;
+			}
 			if (ret != 0) {
 				defers++;
 				pr_warn("%s: overlay destroy failed for #%d\n",