ASoC: omap-hdmi-codec: make the driver common for other SoCs

to support HDMI on CSR SiRFprimaII and atlasVI, we need one more HDMI pseudo
codec, rather than add a new driver, we can make omap HDMI codec common for
other SoCs as well. then the omap-hdmi codec becomes a generic HDMI pseudo-
codec as HDMI audio features depend on HDMI specification not on SoCs.

Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Mark Brown <broonie@linaro.org>