vboot: Add vb2_unpack_key_buffer

Previously, vb2_unpack_key() actually unpacked a key buffer.  Callers
that had a vb2_packed_key had to typecast it back to a uint8_t buffer to
unpack it.  Rename vb2_unpack_key() to vb2_unpack_key_buffer(), and make
vb2_unpack_key() unpack a vb2_packed_key.

BUG=chromium:611535
BRANCH=none
TEST=make runtests; emerge-kevin coreboot depthcharge;
     emerge-samus and boot it

Change-Id: I9ee38a819c59cc58a72ead78cf5ddf3d0f301ae7
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/400906
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
24 files changed