Booting from USB may fail while the macro USB_BOOT_IO_BLOCKS set to 128 because the block size of some USB devices are exceeded 512, like some virtual CD-ROM from BMC, the block size is 2048. So,the count blocks to transfer should be calculated by block size of the USB devices. Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Ming Huang <ming.huang@linaro.org> Reviewed-by: Star Zeng <star.zeng@intel.com> Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>