ARM: OMAP2+: hwmod data: split omap2/3 dispc hwmod class

Currently OMAP2 and 3 share the same omap_hwmod_class and
omap_hwmod_class_sysconfig for dispc. However, OMAP3 has sysconfig
bits that OMAP2 doesn't have, so we need to split those structs into
OMAP2 and OMAP3 specific versions.

This patch only splits the structs, without changing the contents.
This is a prerequisite for a subsequent fix.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
[paul@pwsan.com: added commit note]
Signed-off-by: Paul Walmsley <paul@pwsan.com>