The card debugfs initialization is done in soc_probe but would be better if it
is done when the card in registered

This patch moves the debugfs initialization to register_card()
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Harsha Priya <harsha.priya@intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>