ar71xx: fix leds-rb750 build failure on 2.6.34

SVN-Revision: 22016

target/linux/ar71xx/files/drivers/leds/leds-rb750.c

@@ -12,6 +12,7 @@
 #include <linux/init.h>
 #include <linux/platform_device.h>
 #include <linux/leds.h>
+#include <linux/slab.h>
 
 #include <asm/mach-ar71xx/mach-rb750.h>