mmc: core: don't override the CD GPIO level when "cd-inverted" is set

Since commit 89a5e15b ("gpio/mmc/of: Respect polarity in the device
tree") gpiolib-of parses the "cd-gpios" property and flips the polarity
if "cd-inverted" is also set. This results in the "cd-inverted" property
being evaluated twice, which effectively makes it a no-op:
- first in drivers/gpio/gpiolib-of.c (of_xlate_and_get_gpiod_flags) when
  setting up the CD GPIO
- then again in drivers/mmc/core/slot-gpio.c (mmc_gpio_get_cd) when
  reading the CD GPIO value at runtime

On boards which are using device-tree with the "cd-inverted" property
being set any inserted card are not detected anymore. This is due to the
MMC core treating the CD GPIO with the wrong polarity.

Disable "override_cd_active_level" for the card detection GPIO which is
parsed using mmc_of_parse. This fixes SD card detection on the boards
which are currently using the "cd-inverted" device-tree property (tested
on Meson8b Odroid-C1 and Meson8b EC-100).

This does not remove the CD GPIO inversion logic from the MMC core
because there's at least one driver (sdhci-pci-core for Intel BayTrail
based boards) which still passes "override_cd_active_level = true" to
mmc_gpiod_request_cd(). Due to lack of hardware for testing this is left
untouched.
In the future the GPIO inversion logic for both, card and read-only
detection can be removed once no driver is using it anymore.

Fixes: 89a5e15b

 ("gpio/mmc/of: Respect polarity in the device tree")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Tested-by: Loys Ollivier <loys.ollivier@gmail.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>