ASoC: arizona: Add new common Arizona init function

Currently the driver has quite a few small initialisation functions, in
preparation for some refactoring add a new function arizona_init_common.
This will be used bus probe level initialisation that is common across
Arizona devices. For now just move the notifier chain initialisation in
there.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>