doc: release-notes: document CMSIS-NN upgrade

Update the version update and link to the changelog.

Signed-off-by: Jordan Yates <[email protected]>

doc/releases/release-notes-3.7.rst

@@ -509,6 +509,11 @@ Libraries / Subsystems
   * Mbed TLS was updated to 3.6.0. Release notes can be found at:
     https://github.com/Mbed-TLS/mbedtls/releases/tag/v3.6.0
 
+* 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`,