ASoC: bcm: Refactor to use devm to register cards

The .remove function in many of the BCM drivers just called
snd_soc_unregister_card. Migrate these drivers to use devm to manage
card registration allowing the .remove functions to be eliminated.

Drivers performing other operations in .remove have not been updated.

Signed-off-by: Tim Gover <tim.gover@raspberrypi.org>