Stop AIC23 driver from Oopsing.

Prevent AIC23 driver Oopsing when no AIC23 is present by moving some of the
initialisation to after the chip is found.  There seems to be more that
should be fixed in this driver but with this change it can at least be
compiled into a kernel safely.

Signed-off-by: Andrzej Zaborowski <balrog@zabor.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>