The u-boot code for I2C MAC address retrieval appears to be in file board/davinci/dv-evm/dv_board.c, function misc_init_r(). You'll have to set the ethaddr env var manually before using network commands within u-boot. If you have a backing store (eg. NAND) for u-boot env vars, I guess you could save the MAC addr in the env vars permanently.
In my opinion, do not update the kernel unless you are having problems. For me, the update to 2.6.18 to 2.6.32 was required to get the updated USB and GPIO drivers. Also getting support on this forum is easier with the latest kernel. The jump from 2.6.32 to 2.6.37 or 3.x kernel was not worth for me. I think the pre-built kernels only go up to 2.6.37. The 3.x are a source pull at the TI's Arago GIT. I forgotten how the linux kernel numbers map to the TI PSP version numbers.