ASoC: Rename snd_soc_register_card() to snd_soc_init_card()

Currently ASoC card initialisation is completed by a function called
snd_soc_register_card().  As part of the work to allow independant
registration of cards, codecs and machines in ASoC v2 a new function of
the same name has been added so rename the existing function to
facilitate the merge of v2.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>