mmc: sdhci: dt: Add device tree properties sdhci-caps and sdhci-caps-mask

On some systems the sdhci capabilty register is incorrect for one
reason or another.

The sdhci-caps-mask property specifies which bits in the register
are incorrect and should be turned off before using sdhci-caps to turn
on bits.

The sdhci-caps property specifies which bits should be turned on.

Signed-off-by: Zach Brown <zach.brown@ni.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>