Rebuilding u-boot for Cyrus

The Cyrus defconfigs are Cyrus_P5020_defconfig and Cyrus_P5040_defconfig.

They currently disable size optimization in order to avoid a relocation
bug in some versions of GCC. As the output size is a constant, the size
optimization is not currently important.

Cyrus boots off a microSD card in a slot on the motherboard. This requires
that the u-boot is built for the Pre-Boot Loader on the P5020/P5040.
In order to reflash u-boot, you must download u-boot.pbl, then write it
onto the card. To do that from u-boot:

> tftp 1000000 u-boot.pbl
> mmc write 1000000 8 672

If you want to do this via a card reader in linux:

> dd if=u-boot.pbl of=/dev/sdX bs=512 oseek=8