mfd: arizona: Handle probe deferral for reset GPIO

The Arizona CODECs will generally function correctly without a reset line
although it is strongly advised to have one, as such we do allow the system
to boot if the reset gpio is missing or incorrectly specified.  However
we should fail probe if we get a probe deferral request, this patch adds
handling for this case.

Reported-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>