[M0] 判断SD卡是否存在

适用平台：MTK
适用版本：M

public boolean haveExternelSD(Context context) {
    StorageManager mStorageManager = (StorageManager)context.getSystemService(Context.STORAGE_SERVICE);
    String[] mPathList = mStorageManager.getVolumePaths();
    int size = 0;
    for (int i = 0; i < mPathList.length; i++) {
        if ("mounted".equals(mStorageManager.getVolumeState(mPathList[i]))) {
            size++;
        }
    }
    return size == 1 ? false : true;
}