drm/i915: Move rotated geometry calculations into the fill helper

This way data is available as soon as the view is passed into the call chain.

v2: Store size in bytes instead of pages under the appropriate name. (Chris Wilson)

v3: Use uint64_t instead of size_t. (Daniel Vetter)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> (v2)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>