OMAPDSS: HDMI: support larger register offsets for OMAP5 HDMI core

The HDMI core IP on OMAP5 has a wider address range for registers. The offsets
for the later registers can't fit into the u16 type currently used for hdmi
register read and write functions. Use u32 for offsets instead.

Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>