ARM: dts: am335x-pdu001: Fix polarity of card detection input

When a micro SD card is inserted in the PDU001 card cage, the card
detection switch is opened and the corresponding GPIO input is driven
by a pull-up. Hence change the active level of the card detection
input from low to high.

Signed-off-by: Felix Brack <fb@ltec.ch>
Signed-off-by: Tony Lindgren <tony@atomide.com>