ARM: dts: imx7-colibri: move SD-card to module level

Move SD-card definition to module level. While at it, also disable
write-protect since the Colibri standard does not define a pin for
SD-Card write-protection.

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