release: Zephyr 2.2.0

Bump version to 2.2.0 final.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
diff --git a/VERSION b/VERSION
index d6d7477..7251c26 100644
--- a/VERSION
+++ b/VERSION
@@ -2,4 +2,4 @@
 VERSION_MINOR = 2
 PATCHLEVEL = 0
 VERSION_TWEAK = 0
-EXTRAVERSION = rc3
+EXTRAVERSION =