release: Zephyr 2.1.0-rc3

Bumped to v2.1.0-rc3

Signed-off-by: David Leach <david.leach@nxp.com>
diff --git a/VERSION b/VERSION
index 053f539..7dd26f6 100644
--- a/VERSION
+++ b/VERSION
@@ -2,4 +2,4 @@
 VERSION_MINOR = 1
 PATCHLEVEL = 0
 VERSION_TWEAK = 0
-EXTRAVERSION = rc2
+EXTRAVERSION = rc3