arm: dts: mt7623: fix card detection issue on bananapi-r2

Fix that bananapi-r2 booting from SD-card would fail since incorrect
polarity is applied to the previous setup with GPIO_ACTIVE_HIGH.

Cc: stable@vger.kernel.org
Fixes: 0eed8d09 ("arm: dts: mt7623: Add SD-card and EMMC to bananapi-r2")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Tested-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>