drm/armada: provide pitches from armada_drm_plane_calc_addrs()

Provide the framebuffer pitches from armada_drm_plane_calc_addrs() as
well as the base addresses for each plane.  Since this is now about
more than just addresses, rename to armada_drm_plane_calc().

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>