drivers/char: Add module.h to those who were using it implicitly

A pending cleanup will mean that module.h won't be implicitly
everywhere anymore.  Make sure the modular drivers in char are
actually calling out for <module.h> explicitly in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/char/hw_random/virtio-rng.c

@@ -23,6 +23,7 @@
 #include <linux/spinlock.h>
 #include <linux/virtio.h>
 #include <linux/virtio_rng.h>
+#include <linux/module.h>
 
 static struct virtqueue *vq;
 static unsigned int data_avail;