dtc: Bump version to v1.4.6

We've accumulated a number of bugfixes since v1.4.5, so prepare for another
release.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/Makefile b/Makefile
index e1e138a..9ba8121 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@
 #
 VERSION = 1
 PATCHLEVEL = 4
-SUBLEVEL = 5
+SUBLEVEL = 6
 EXTRAVERSION =
 LOCAL_VERSION =
 CONFIG_LOCALVERSION =