ARM: pxa/tosa: register wm9712 codec device

Since f0fba2ad it's required to register platform devices even for
AC'97 codecs. Register one on tosa (wm9712-codec).

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>