vboot: Move IsEntryUnused to gpt_misc

Over in depthcharge, IsEntryUnused will be useful for presenting the
partition table to the kernel. This patch moves that function to
gpt_misc.[ch] for export to depthcharge.

TEST=Booted a kernel on NAND with all this compiled in
TEST=make runtests passed
BRANCH=none
BUG=none

Signed-off-by: Dan Ehrenberg <dehrenberg@google.com>
Change-Id: I56445d1a420fec4d8385ddffc5469b7d77eab576
Reviewed-on: https://chromium-review.googlesource.com/231455
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Commit-Queue: Daniel Ehrenberg <dehrenberg@chromium.org>
Tested-by: Daniel Ehrenberg <dehrenberg@chromium.org>
5 files changed