docs: Add release note snippet on MCUBOOT_HW_KEY for image encryption

Signed-off-by: Dinesh Kumar K <dinesh@linumiz.com>
diff --git a/docs/release-notes.d/bootutil-enc-hw-keys.md b/docs/release-notes.d/bootutil-enc-hw-keys.md
new file mode 100644
index 0000000..2640b67
--- /dev/null
+++ b/docs/release-notes.d/bootutil-enc-hw-keys.md
@@ -0,0 +1,2 @@
+- Added support for retrieving hw embed private keys for image encryption
+  (The private key can be retrieved from trusted sources like OTP, TPM.).