release: Zephyr v3.6.0-rc1

Sets the version to v3.6.0-rc1.

Signed-off-by: Maureen Helm <maureen.helm@analog.com>
diff --git a/VERSION b/VERSION
index a2cbf5c..0e779c2 100644
--- a/VERSION
+++ b/VERSION
@@ -1,5 +1,5 @@
 VERSION_MAJOR = 3
-VERSION_MINOR = 5
-PATCHLEVEL = 99
+VERSION_MINOR = 6
+PATCHLEVEL = 0
 VERSION_TWEAK = 0
-EXTRAVERSION =
+EXTRAVERSION = rc1