drm/i915: Stuff rotation params into view union

We don't need 2 separate unions.

Note that this was done intentinoally

Author: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Date:   Wed May 6 14:35:38 2015 +0300

    drm/i915: Add a partial GGTT view type

on Tvrtko's request, but without a clear justification. Rotated views
are also not checking for matching paramters in i915_ggtt_view_equal,
which seems like a bug. But this patch here doesn't change that.

Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1444834266-12689-2-git-send-email-daniel.vetter@ffwll.ch
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>