ppc4xx: Updates to Korat-specific code

ppc4xx: Updates to Korat-specific code

This patch contains updates for changes for the Korat PPC440EPx board.
These changes include:

(1) Support for "permanent" and "upgradable" copies of U-Boot, as
described in the new "doc/README.korat" file;

(2) a new memory map for the registers in the board's CPLD;

(3) a revised format for manufacturer's data in serial EEPROM; and

(4) changes to track updates to U-Boot for the Sequoia board.

Signed-off-by: Larry Johnson <lrj@acm.org>