mmc: jz4740: Get CD/WP GPIOs from descriptors

mmc: jz4740: Get CD/WP GPIOs from descriptors

Modifty the JZ4740 driver to retrieve card detect and write
protect GPIO pins from GPIO descriptors instead of hard-coded
global numbers. Augment the only board file using this in the
process and cut down on passed in platform data.

Preserve the code setting the caps2 flags for CD and WP
as active low or high since the slot GPIO code currently
ignores the gpiolib polarity inversion semantice and uses
the raw accessors to read the GPIO lines, but set the right
polarity flags in the descriptor table for jz4740.

Cc: Paul Cercueil <paul@crapouillou.net>
Cc: linux-mips@linux-mips.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Paul Burton <paul.burton@mips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>