SYSLINK: sysmgr - ioctl call to stopcallback sets return status

In sysmgr_ioctl, the execution of CMD_SYSMGR_STOPCALLBACK does not set the
return value in cargs.api_status.  This caused an error sometimes because the
status was uninitialized.  Now it sets the status to 0 just like for the cases
of CMD_SYSMGR_LOADCALLBACK and CMD_SYSMGR_STARTCALLBACK.  Note that since the
platform callbacks return void, we must set the api_status manually.
Signed-off-by: Simon Que <sque@ti.com>

drivers/dsp/syslink/multicore_ipc/sysmgr_ioctl.c

@@ -120,6 +120,7 @@ int sysmgr_ioctl(struct inode *inode, struct file *filp,
 	case CMD_SYSMGR_STOPCALLBACK:
 #if defined CONFIG_SYSLINK_USE_SYSMGR
 		platform_stop_callback((void *)(cargs.args.proc_id));
+		cargs.api_status = 0;
 #endif
 		break;
 	default: