Preps for 1.8.0

Update version fields for 1.8.0 release.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/docs/release-notes.md b/docs/release-notes.md
index 0b3e01c..885fe31 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -30,6 +30,8 @@
   top level directory.
 - Fault injection tests use updated TF-M.
 - Thingy:53 now supports multi-image DFU.
+- ram load and image encryption can be used together, allowing the
+  entire contents of flash to always remain encrypted.
 
 ### Security fixes