Fix grub2 compile errors.

grub2 does not compile due to strict warning checks. This is fixed by
removing variables that are declared + assigned but never used.

BUG=32776.
TEST=configure / make, copy grub-mkimage binary, then build_image.

Change-Id: I9fe488c06edcde01dfdf244773323a2088285879
Reviewed-on: https://gerrit.chromium.org/gerrit/27961
Tested-by: Shawn Nematbakhsh <shawnn@chromium.org>
Commit-Ready: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-by: Micah Catlin <micahc@chromium.org>
8 files changed