nand: vboot support for small GPTs

This patch makes some small modifications to cgpt and vboot to
root out the last vestigates of a fixed 128-entry GPT:
- Get rid of the TOTAL_ENTRIES_SIZE constant and all users.
- Reduce MAX_NUMBER_OF_ENTRIES to 128 (which is what the GPT
  spec specifies) so that this can be used for things like memory
  allocations without additional overhead.
- Base the amount of GPT read/written on the number of entries
  specified in the GPT header on disk/flash.

BUG=chromium:433433
TEST=make runalltests
TEST=Modified fmap to make an 8k RW_GPT, wrote a GPT with cgpt, then
rebooted and found that the GPT was correctly read after restarting
and the appropriate mtd partitions were present.
BRANCH=none

Change-Id: I45317377da20259caf04a7a4fa077a892b03c45f
Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/238245
Reviewed-by: Randall Spangler <rspangler@chromium.org>
7 files changed