Use correct spelling of "U-Boot"

Correct spelling of "U-Boot" shall be used in all written text
(documentation, comments in source files etc.).

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Minkyu Kang <mk7.kang@samsung.com>

* Patch by Jon Loeliger, 2005-05-05
Implemented support for MPC8548CDS board.
Added DDR II support based on SPD values for MPC85xx boards.
This roll-up patch also includes bugfies for the previously
published patches:
DDRII CPO, pre eTSEC, 8548 LBIU, Andy's TSEC, eTSEC 3&4 I/O

Patches by Scott McNutt, 24 Aug 2004:
- Add support for Altera Nios-II processors.
- Add support for Psyent PCI-5441 board.
- Add support for Psyent PK1C20 board.

Patches by Jon Loeliger, 24 Aug 2004:
- Add support for the MPC8541 and MPC8555 CDS boards
- Cleanup eth?addr handling: make dependent on CONFIG_ETH?ADDR