It can be handy to get the number of planes for this pipe, ie including
the primary plane to loop over them. Introduce a little function to do
so.
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>