ARM: OMAP: hsmmc: board-sdp4430: declare support for MMC_PM_KEEP_POWER

Declare support for keeping the power of the wlan chip
while suspended. this is needed for Wakeup-On-Wireless.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>