hwrng: omap3-rom - Include linux/io.h for virt_to_phys

This patch adds linux/io.h to the header list to ensure that we
get virt_to_phys on all architectures.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/drivers/char/hw_random/omap3-rom-rng.c b/drivers/char/hw_random/omap3-rom-rng.c
index e08a888..a431c5c 100644
--- a/drivers/char/hw_random/omap3-rom-rng.c
+++ b/drivers/char/hw_random/omap3-rom-rng.c
@@ -18,6 +18,7 @@
 #include <linux/workqueue.h>
 #include <linux/clk.h>
 #include <linux/err.h>
+#include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>