omap: Beagle: no gpio_wp pin connection on xM

The omap3630 based BeagleBoard xM uses a MicroSD card slot with
no write protection.

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>