File \USB_HOST\Target\usbh_conf.h has the definitions:
#define USBH_malloc malloc
#define USBH_free free
This does not work with FreeRTOS. It will be better, but maybe not perfect:
/** Alias for memory allocation. */
#if (USBH_USE_OS == 1)
#define USBH_malloc pvPortMalloc
#else
#define USBH_malloc malloc
#endif
/** Alias for memory release. */
#if (USBH_USE_OS == 1)
#define USBH_free vPortFree
#else
#define USBH_free free
#endif
