Update two oddball NAND commands to work with {offset, length}
instead of block numbers, matching the other commands as well
as usage in U-Boot and the Linux-MTD utilities.

Document them accordingly.  Update the single in-tree use of
those commands (sheevaplug).

ALSO:

 (a) Document the current 2 GByte/chip ceiling for NAND chipsize.
     (32 bit offset/length values can't represent 4 GBytes.)  Maybe
     after the upcoming release, the code can switch to 64-bits.

 (b) The "nand check_bad_blocks" should report "bad" blocks.  They
     are not "invalid" blocks; they're "bad" ones.

 (c) Tweak the "nand info" command to handle the "no arguments"
     case sanely (show everything, instead of showing garbage) and
     not listing the blocksize in hex kbytes (duh).


git-svn-id: svn://svn.berlios.de/openocd/trunk@1904 b42882b7-edfa-0310-969c-e2dbd0fdcd60