beaglebone uEnv.txt changes

21c21,23
< mmcroot=/dev/mmcblk0p2 ro
---
> bootdev=0:1
>
> mmcroot=/dev/sda3 ro
24,26c26,28
< loadkernel=load mmc ${mmcdev}:${mmcpart} 0x80300000 ${kernel_file}
< loadinitrd=load mmc ${mmcdev}:${mmcpart} 0x81600000 ${initrd_file}; setenv initrd_size ${filesize}
< loadfdt=load mmc ${mmcdev}:${mmcpart} 0x815f0000 /dtbs/${fdtfile}
---
> loadkernel=load usb ${bootdev} 0x80300000 ${kernel_file}
> loadinitrd=load usb ${bootdev} 0x81600000 ${initrd_file}; setenv initrd_size ${filesize}
> loadfdt=load usb ${bootdev} 0x815f0000 /dtbs/${fdtfile}
34c36
< uenvcmd=run boot_ftd; run device_args; bootz 0x80300000 0x81600000:${initrd_size} 0x815f0000
---
> uenvcmd=usb start; run boot_ftd; run device_args; bootz 0x80300000 0x81600000:${initrd_size} 0x815f0000