staging: media: atomisp: add missing include in vlv2_plat_clock.c

To use IO functions like writel, readl, ioremap_nocache and iounmap,
linux/io.h should be included.
Signed-off-by: Jérémy Lefaure <jeremy.lefaure@lse.epita.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/media/atomisp/platform/clock/vlv2_plat_clock.c

@@ -20,6 +20,7 @@
  */
 
 #include <linux/err.h>
+#include <linux/io.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include "../../include/linux/vlv2_plat_clock.h"