leds: leds-net48xx: Use linux/io.h instead of asm/io.h

Fixes the following checkpatch warning:
WARNING: Use #include <linux/io.h> instead of <asm/io.h>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

drivers/leds/leds-net48xx.c

@@ -15,7 +15,7 @@
 #include <linux/platform_device.h>
 #include <linux/leds.h>
 #include <linux/err.h>
-#include <asm/io.h>
+#include <linux/io.h>
 #include <linux/nsc_gpio.h>
 #include <linux/scx200_gpio.h>
 #include <linux/module.h>