nand: Allow smaller disks for booting a kernel
nand: Allow smaller disks for booting a kernel

When vboot eliminates trivially small disks, it checks the GPT size for
external GPT disks. For upcoming NAND devices, the GPT size is 8kB. This
patch changes the definition of trivially small disks to be those under
8kB so that NAND can be booted from.

BUG=chromium:433433
TEST=make runalltests
TEST=Booted and saw a kernel from NAND selected on from an 8kB GPT.
BRANCH=none

Change-Id: I5047b9b642d564d5e4d77dd0b6dafb9eea09176a
Signed-off-by: Dan Ehrenberg <7651083733dec1b497ee3fb7d4e25811aa64d643@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/238463
Reviewed-by: Bill Richardson <129945214b1d548d8e49b6c29c43094f8c78057f@chromium.org>
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

geekboxzone/mmallow_external_vboot_reference,acorn-marvell/vboot_reference,acorn-marvell/vboot_reference,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,acorn-marvell/vboot_reference,acorn-marvell/vboot_reference,geekboxzone/mmallow_external_vboot_reference,geekboxzone/mmallow_external_vboot_reference,geekboxzone/mmallow_external_vboot_reference,geekboxzone/mmallow_external_vboot_reference,coreboot/vboot