Fix coreboot table size calculations.

The code when reporting the coreboot table size did not account
for the last added table record. This change fixes the problem.

 . rebuild coreboot, program it on the target, restart it
 . look for 'Wrote coreboot table at:' in the console log
 . observe the adequate table size reported

 $  grep 'Wrote coreboot table:' /tmp/cb.log
 Wrote coreboot table at: 00000500, 0x10 bytes, checksum c06f
 Wrote coreboot table at: 7f6fc000, 0x1a73 bytes, checksum 3e45
 $

Change-Id: Ic55501a4ae06fab2bcda9aea58e362325f2edccf
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: http://review.coreboot.org/703
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>