在u-boot下通过tftp烧写内核和文件系统，内核载入时卡住

引用: updatesys=nand erase.chip;mmc dev 0; mmc rescan; fatload mmc 0 0x82000000 MLO;                                 nand write 0x82000000 0 ${filesize};fatload mmc 0 0x82000000 myd_c335x.dtb;         nand write 0x82000000 0x80000 ${filesize};fatload mmc 0 0x82000000 u-boot.img;                 nand write 0x82000000 0xc0000 ${filesize};fatload mmc 0 0x82000000 zImage;                         nand write 0x82000000 0x200000 ${filesize};fatload mmc 0 0x82000000 rootfs.ubi;                 nand write 0x82000000 0xa00000 ${filesize};mtdids=nand0=nand.0