ASoC: OMAP: HDMI: Make build config options more generic

Make Kconfig and Makefile more generic to encompass not only
OMAP4 but other OMAP processors featuring HDMI.

Also, relax the dependency list to depend only on any OMAP processor
supporting OMAP2_DSS and OMAP4_DSS_HDMI. As HDMI support for
future OMAP versions is added, the dependency list must change
accordingly.

Signed-off-by: Ricardo Neri <ricardo.neri@ti.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@ti.com>