doc: release-notes: document CMSIS-NN upgrade

Update the version update and link to the changelog.

Signed-off-by: Jordan Yates <jordan@embeint.com>

Author: JordanYates

doc/releases/release-notes-3.7.rst

@@ -851,6 +851,11 @@ Libraries / Subsystems
     for the Mbed TLS's p256-m driver PSA crypto library. This is a Cortex-M SW
     optimized implementation of secp256r1 curve.
 
+* CMSIS-NN
+
+  * CMSIS-NN was updated to v6.0.0 from v4.1.0:
+    https://arm-software.github.io/CMSIS-NN/latest/rev_hist.html
+
 * Random
 
   * Besides the existing :c:func:`sys_rand32_get` function, :c:func:`sys_rand8_get`,