powerpc/dts: Correct sdhci quirk for bsc9131

We use property "sdhci,auto-cmd12" instead of "fsl,sdhci-auto-cmd12"
to distinguish if the sdhc host has quirk SDHCI_QUIRK_MULTIBLOCK_READ_ACMD12.

Signed-off-by: Haijun Zhang <Haijun.Zhang@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>