ARM: dts: meson8b: odroidc1: mark the SD card detection GPIO active-low

After commit 89a5e15b ("gpio/mmc/of: Respect polarity in the device
tree") SD cards are not detected anymore.

The CD GPIO is "active low" on Odroid-C1. The MMC dt-bindings specify:
"[...] using the "cd-inverted" property means, that the CD line is active
high, i.e. it is high, when a card is inserted".

Fix the description of the SD card by marking it as GPIO_ACTIVE_LOW and
drop the "cd-inverted" property. This makes the definition consistent
with the existing dt-bindings and fixes the check whether an SD card is
inserted.

Fixes: e03efbce ("ARM: dts: meson8b-odroidc1: add microSD support")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>