drm/i915: Use GGTT view when (un)pinning objects to planes

To support frame buffer rotation we need to be able to pass on the information
on what kind of GGTT view is required for display.

This patch just adds the parameter and makes all the callers default to the
normal view.

v2: Rebased for ggtt view changes.
v3: Don't limit PIN_MAPPABLE to normal views just yet. (Joonas Lahtinen)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> (v3)
[danvet: s/BUG/WARN/ in the patch hunk because. At least where the
BUG_ON isn't fatal right away.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>