dt-bindings: mmc: sdhci-pxa: restrict pinctrl to pxav1

dt-bindings: mmc: sdhci-pxa: restrict pinctrl to pxav1

The current pinctrl properties apply only to the pxav1 controller.
Adding one default pinctrl node to a pxav3 controller therefore causes
a schema warning.

Check the existing properties only on pxav1. pxav2 and pxav3 may add
their own set of pinctrl properties if and when needed.

Signed-off-by: Duje Mihanović <duje@dujemihanovic.xyz>
Link: https://lore.kernel.org/r/20250708-pxa1908-lkml-v16-1-b4392c484180@dujemihanovic.xyz
Signed-off-by: Arnd Bergmann <arnd@arndb.de>