[nrf fromtree] manifest: Update nrf hw models to latest

* Update the HW models module to
6b6ae3652c92c95edd945dce6ad9ef9892aab89b

Including the following:
* 6b6ae36 UART: Minor optimization
* afe84c1 fake timer: Minor speed optimization for nrf52
* a5a4dfd RTC: Fix counter value when CLEAR after STOP

Signed-off-by: Alberto Escolar Piedras <[email protected]>
(cherry picked from commit 33d4b6d)
Signed-off-by: Ivan Iushkov <[email protected]>

Author: aescolar

west.yml

@@ -295,7 +295,7 @@ manifest:
       groups:
         - tools
     - name: nrf_hw_models
-      revision: a08acc7d3a853f890df2bf82167c02ab2153ffe7
+      revision: 6b6ae3652c92c95edd945dce6ad9ef9892aab89b
       path: modules/bsim_hw_models/nrf_hw_models
     - name: open-amp
       revision: 214f9fc1539f8e5937c0474cb6ee29b6dcb2d4b8