ARM: dts: bcm283x: Fix hdmi hpd gpio pull

Raspberry pi board model B revison 2 have the hot plug detector gpio
active high (and not low as it was in the dts).

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Fixes: 49ac67e0

 ("ARM: bcm2835: Add VC4 to the device tree.")
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>