usb/core: switch to usb warning code

usb/core: switch to usb warning code

BZ: 39874

Use warning code will be more readable.

Change-Id: I8edbe195223bef323f6f1f4799e0c1dd8f656583
Signed-off-by: Wu, Hao <hao.wu@intel.com>
Reviewed-on: http://android.intel.com:8080/51548
Reviewed-by: Tang, Richard <richard.tang@intel.com>
Reviewed-by: Tang, Jianqiang <jianqiang.tang@intel.com>
Reviewed-by: Meng, Zhe <zhe.meng@intel.com>
Tested-by: Meng, Zhe <zhe.meng@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>