hd-geometry: Cut out block layer translation middleman

hd-geometry: Cut out block layer translation middleman

hd_geometry_guess() picks geometry and translation.  Callers can get
the geometry directly, via parameters, but for translation they need
to go through the block layer.

Add a parameter for translation, so it can optionally be gotten just
like geometry.  In preparation of purging translation from the block
layer, which will happen later in this series.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>