mmc: arm_pl180_mmci: Remove cd_inverted host's struct field

As platform uses GPIOs for card detection, it's
simpler and more readable to use GPIO_ACTIVE_(LOW|HIGH)
in the gpio flags instead of using the cd-inverted
property.

Reported-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>