ASoC: ux500: Provide better checking for Device Tree and/or Platform Data

These drivers will not work without platform specific data, which is
passed in via Device Tree or Platform Data. To avoid the chance of
NULL pointer dereferencing and alike, let's ensure we have at least
one of the methods in play before continuing.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>