ASoC: davinci: kconfig: Prepare for AM43xx support

AM43xx have the same McASP IP as AM33xx and both platform uses eDMA. Modify
the Kconfig so it will be possible to add audio support for AM43xx based
boards later.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>