drm/i915: Remove mostly unused variable in intel_rotate_fb_obj_pages

It is only used in logging and it doesn't need to exist on its own.

Also it was misleading to log view size as object size.

v2: Improve commit message. (Joonas Lahtinen)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
[danvet: s/%lu/%zu/ where needed, reported by 0-day.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>