updating u-boot_2013.07.bb recipe

[Cédric Le Goater]

Hello. 

The uboot recipe in openbmc is still at 4b44678c11. Without them, I see 
memory corruption under qemu, so I suppose this is the same for real HW. 

commit 6f7818cdb8d8 "net: aspeednic: Do not start hardware in initialize"
seems to solve the problem. 

Is there a reason for staying at that level in uboot ? Could we take all
Milton's patches in ? 

Thanks,

C.