release: Zephyr 2.1.0-rc1

Bumped to v2.1.0-rc1

Signed-off-by: David Leach <david.leach@nxp.com>
diff --git a/VERSION b/VERSION
index b0d2c13..f654d99 100644
--- a/VERSION
+++ b/VERSION
@@ -1,5 +1,5 @@
 VERSION_MAJOR = 2
-VERSION_MINOR = 0
-PATCHLEVEL = 99
+VERSION_MINOR = 1
+PATCHLEVEL = 0
 VERSION_TWEAK = 0
-EXTRAVERSION =
+EXTRAVERSION = rc1