ARM: dts: vf-colibri: disable write-protection for SD-card

The Colibri standard does not define a pin for SD-Card write-
protection. Use the disable-wp property to indicate that there
is no physical WP line present.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>