ARM: OMAP: Activate MPU retention code in omap2/pm.c

FIXME section in function omap2_allow_mpu_retention didn't allow MPU to
enter into retention even if system was idle. MPU retention works fine at
least in Nokia N800.
Signed-off-by: Jarkko Nikula <jarkko.nikula@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/pm.c

@@ -573,8 +573,7 @@ static int omap2_allow_mpu_retention(void)
 	if (sti_console_enabled)
 		return 0;
 
-	/* FIXME: Enable soon */
-	return 0;
+	return 1;
 }
 
 static void omap2_enter_mpu_retention(void)