HI,
[ 0.000000] Kernel command line: mem=56M console=ttyS1,115200n8 root=/dev/ram0 rw initrd=0x82000000,20M ip=dhcp eth=$(ethaddr)
As per your bootargs, Your are trying to boot your board with ramdisk,
1) Ensure you got ramdisk from anyother media and copied to RAM addr (0x82000000)
Ex:
copy your ramdisk.gz file into tftpboot dir of your host
u-boot # tftp 0x82000000 ramdisk
u-boot # boot
2) If you want to access filsystem through NFS mode
Ex:
copy & extract your filesystem into NFS folder in your host machine & export it
Refer this TI wiki link to know more