release-notes: Add note on zcbor encoder fix

Adds a note that the zcbor encoder buffer size has been fixed.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>
diff --git a/docs/release-notes.d/zcbor-fix.md b/docs/release-notes.d/zcbor-fix.md
new file mode 100644
index 0000000..6f191df
--- /dev/null
+++ b/docs/release-notes.d/zcbor-fix.md
@@ -0,0 +1,3 @@
+- Fixed an issue with the boot_serial zcbor setup encoder function
+  wrongly including the buffer address in the size which caused
+  serial recovery to fail on some platforms.