sound/aoa: Adapt to new i2c probing scheme

The i2c-powermac driver now creates the i2c devices properly
from the device-tree, including workarounds for broken or
missing device-tree bits, so let's just use the normal probe
methods and get rid of the hand made device creation code.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>