sof/ipc/msg.h: add missing #include <ipc/trace.h>

`msg.h` needs `ipc/trace.h` for `sof_ipc_dma_trace_posn`

Fixes commit b91e253f65 ("include: sof: debug: Split panic.h into
Zephyr and XTOS-specific headers") that broke `scripts/fuzz.sh` because
it stopped `ipc/msg.h` from accidentally getting `ipc/trace.h` through
`panic.h`.

Fixes:

```
src/include/sof/ipc/msg.h:146:34: warning: declaration of
  'struct sof_ipc_dma_trace_posn' will not be visible outside
  of this function [-Wvisibility]
void ipc_build_trace_posn(struct sof_ipc_dma_trace_posn *posn);
```

```
sof/src/trace/dma-trace.c:160:23: warning: incompatible pointer
types passing 'struct sof_ipc_dma_trace_posn *' to parameter of
type 'struct sof_ipc_dma_trace_posn *' [-Wincompatible-pointer-types]
        ipc_build_trace_posn(&sof->dmat->posn);
                             ^~~~~~~~~~~~~~~~
sof/zephyr/../src/include/sof/ipc/msg.h:146:58: note: passing argument
 to parameter 'posn' here
void ipc_build_trace_posn(struct sof_ipc_dma_trace_posn *posn);
```

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

src/include/sof/ipc/msg.h

@@ -21,6 +21,8 @@
 #include <rtos/spinlock.h>
 #include <sof/trace/trace.h>
 #include <sof/ipc/common.h>
+#include <ipc/trace.h>
+
 #include <stdbool.h>
 #include <stdint.h>