mmc: sdhci-pxav3: dt: Support "cd-gpios" property

Tested on OLPC XO-4/MMP3, where the card detection pin for one of
the controllers is a sideband GPIO.  The third cell in the cd-gpios
property controls whether the GPIO is active high/active low.

(Also, pass host_caps2 through from platdata to the mmc host.)

Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
[kliu5@marvell.com: Compile fix]
Signed-off-by: Chris Ball <cjb@laptop.org>