ASoC: ams-delta: Convert to use snd_soc_register_card()

The old method of registering with the ASoC core by creating a
"soc-audio" platform device no longer works for Amstrad Delta sound card
after recent changes to drvdata handling (commit
0998d063, 'device-core: Ensure drvdata =
NULL when no driver is bound'.

Use snd_soc_register_card() method instead, as suggested by the ASoC
core generated warning message, and move both the card and codec
platform device registration to the arch board file where those belong.

Created and tested against linux-3.6-rc5.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>