Clean-up of cpu_arm920t and cpu_arm920t_s3c24x0 code

This patch re-formats the code in cpu/arm920t and cpu/arm920t/23c24x0 in
preparation for changes to add support for the Embest SBC2440-II Board.

The changes are as follows:
- re-indent the code using Lindent
- make sure register layouts are defined using a C struct
- replace the upper-case typedef'ed C struct names with lower case
  non-typedef'ed ones
- make sure registers are accessed using the proper accessor functions
- run checkpatch.pl and fix any error reports

It assumes the following patch has been applied first:
- [U-Boot][PATCH-ARM] CONFIG_SYS_HZ fix for ARM902T S3C24X0 Boards, 05/09/2009

Tested on an Embest SBC2440-II Board with local u-boot patches as I don't have
any s3c2400 or s3c2410 boards but need this patch applying before I can submit
patches for the SBC2440-II Board. Also, ran MAKEALL for all ARM9 targets and no
new warnings or errors were found.

Signed-off-by: Kevin Morfitt <kevin.morfitt@fearnside-systems.co.uk>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>