ASoC: soc core allow machine driver to register the card

The machine driver can't register the card directly and need to do this thru
soc-audio device creation

This patch allows the register and unregister card to be directly called by
machine drivers

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Harsha Priya <priya.harsha@intel.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>