tests: ipc: Update exclude platforms

remove qemu_xtensa from exclude platforms as fix for this platform
is provided.

add ast1030_evb to exclude platforms as this soc does not yet have
in tree driver for external cache controller.

Signed-off-by: Emil Obalski <[email protected]>

Author: Emil Obalski

tests/subsys/ipc/icmsg_buf/testcase.yaml

@@ -2,4 +2,4 @@ tests:
   subsys.ipc.icmsg_buf:
     integration_platforms:
       - nrf5340dk_nrf5340_cpuapp
-    platform_exclude: qemu_xtensa qemu_malta
+    platform_exclude: qemu_malta ast1030_evb