manifest: Update sdk-zephyr revision

Update sdk-zephyr revision to remove
POSIX_MULTI_PROCESS from POSIX_SIGNALS.
so it can be disabled in config.

Signed-off-by: Kapil Bhatt <kapil.bhatt@nordicsemi.no>

Author: kapbh

west.yml

@@ -65,7 +65,7 @@ manifest:
     # https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/guides/modules.html
     - name: zephyr
       repo-path: sdk-zephyr
-      revision: 542443e079bb838d39dd5bdde184f3e3165ea230
+      revision: e321c108d04e2f192b55a90de850e182ec5cb553
       import:
         # In addition to the zephyr repository itself, NCS also
         # imports the contents of zephyr/west.yml at the above