ARM: dts: am572x-idk: Fix GPIO polarity for MMC1 card detect

The GPIO polarity for MMC1 card detect is set to '0' which means
active-high. However the polarity should be active-low. Fix it
here.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>