manifest: hal_atmel: Bump HAL Atmel hash

Needed for the winc1500 driver in hal_atmel to be compatible with
 POSIX enabled.

Signed-off-by: Andreas Ålgård <aal@ixys.no>

west.yml

@@ -152,7 +152,7 @@ manifest:
       groups:
         - hal
     - name: hal_atmel
-      revision: 56d60ebc909ad065bf6554cee73487969857614b
+      revision: pull/42/head
       path: modules/hal/atmel
       groups:
         - hal