drm/i915: Setup clipped src/dest coordinates during FB reconstruction (v2)

drm/i915: Setup clipped src/dest coordinates during FB reconstruction (v2)

Plane state objects contain two copies of src/dest coordinates:  the
original (requested by userspace) coordinates in the base
drm_plane_state object, and a second, clipped copy (i.e., what we
actually want to program to the hardware) in intel_plane_state.  We've
only been setting up the former set of values during boot time FB
reconstruction, but we should really be initializing both.

Note that the code here probably still needs some more work since we
make a lot of assumptions about how the BIOS programmed the hardware
that may not always be true, especially on gen9+; e.g.,
 * Primary plane might not be positioned at 0,0
 * Primary plane could have been rotated by the BIOS
 * Primary plane might be scaled
 * The BIOS fb might be a single "extended mode" FB that spans
   multiple displays.
 * ...etc...

v2: Reword/expand commit message description of assumptions we make

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by(v1): Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449171462-30763-4-git-send-email-matthew.d.roper@intel.com
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>