omap: zoom: add fixed regulator device for wlan

Add a fixed regulator vmmc device to enable power control
of the wl1271 wlan device.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>