drm/i915/skl: Take 90/270 rotation into account in watermark calculations

v2: Pass in rotation info to sprite plane updates as well.

v3: Use helper to determine 90/270 rotation. (Michel Thierry)

v4: Rebased for fb modifiers and atomic changes.

For: VIZ-4546
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com> (v3)
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>