When using the universal plane interface, the source rectangle
coordinates define the panning offset for the primary plane, which needs
to be stored in crtc->{x,y}.  The original universal plane code
negelected to set these panning offset fields, which was partially
remedied in:

        commit ccc759dc
        Author: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
        Date:   Wed Sep 24 14:20:22 2014 -0300

            drm/i915: Merge of visible and !visible paths for primary planes

However the plane source coordinates are provided in 16.16 fixed point
format and the above commit forgot to convert back to integer
coordinates before saving the values.  When we replace
intel_pipe_set_base() with plane->funcs->update_plane() in a future
patch, this bug becomes visible via the set_config entrypoint as well as
update_plane.

Cc: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Testcase: igt/kms_plane
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>