dm: cleanup assert in core.c

- check input by condition check, instead of assert.
 - remove redundant header file including for some files.

Tracked-On: #3252
Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>
Reviewed-by: Shuo Liu <shuo.a.liu@intel.com>

devicemodel/hw/platform/usb_pmapper.c

@@ -8,7 +8,6 @@
 
 #include <pthread.h>
 #include <stdio.h>
-#include <assert.h>
 #include <string.h>
 #include <unistd.h>
 #include "usb.h"