ARM: OMAP5: hwmod: set DSS submodule parent hwmods

Set DSS core hwmod as the parent for all the DSS submodules.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Archit Taneja <archit.taneja@gmail.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>