vboot: move lib20/packed_key.c into 2lib namespace

lib20/packed_key.c functions are currently called throughout
2lib namespace, so move to 2lib/2packed_key.c.

Move function declarations from vb2_common.h to 2packed_key.h,
and include 2packed_key.h from 2common.h.

BUG=b:124141368, chromium:968464
TEST=make clean && make runtests
BRANCH=none

Signed-off-by: Joel Kitching <kitching@google.com>
Change-Id: I151b2d41cbbfa1bfd03de301bd4ee69c49e81f3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2635220
Tested-by: Joel Kitching <kitching@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
27 files changed