release: Zephyr 2.0.0-rc2

Bump to 2.0.0-rc2.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
diff --git a/VERSION b/VERSION
index c359e4c..e91ccea 100644
--- a/VERSION
+++ b/VERSION
@@ -2,4 +2,4 @@
 VERSION_MINOR = 0
 PATCHLEVEL = 0
 VERSION_TWEAK = 0
-EXTRAVERSION = rc1
+EXTRAVERSION = rc2