ASoC: p1022ds: add support for fsl,P1022 and fsl,P1022DS model names

Commit ab827d97 ("powerpc/85xx: Rework P1022DS device tree") renamed the
the /model property of the P1022DS device tree from "fsl,P1022" to
"fsl,P1022DS".  To support both old and new device trees, the ASoC
machine driver for the P1022DS needs to query the /model property and
update the platform driver object dynamically.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>