ARM: AM43xx: hwmod: add DSS hwmod data

Add DSS hwmod data for AM43xx.

Signed-off-by: Sathya Prakash M R <sathyap@ti.com>
[tomi.valkeinen@ti.com: added missing dispc flags]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Rajendra Nayak <rnayak@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Felipe Balbi <balbi@ti.com> # on linux-next 5f295cdf5c5d
[paul@pwsan.com: fixed build break on AM43xx-only config]
Signed-off-by: Paul Walmsley <paul@pwsan.com>