dtc: Update to version 1.6.1

The dtc submodule is currently pointing to non-release commit. It's nicer
if submodules point to release versions instead and since dtc 1.6.1 is
available now, let's update to that version.

Message-Id: <20210827120901.150276-4-thuth@redhat.com>
Acked-by: Greg Kurz <groug@kaod.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Thomas Huth <thuth@redhat.com>

diff --git a/dtc b/dtc
index 85e5d839847af54efab170f2b1331b2a6421e647..b6910bec11614980a21e46fbccc35934b671bd81 160000 (submodule)
--- a/dtc
+++ b/dtc
@@ -1 +1 @@
-Subproject commit 85e5d839847af54efab170f2b1331b2a6421e647
+Subproject commit b6910bec11614980a21e46fbccc35934b671bd81