[ARM] pxa/spitz: Correctly register WM8750

This patch registers the WM8750 codec on a proper place on the SPITZ machine
after the WM8750 driver was converted to new API.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>