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

The device.h header was including module.h, making it present for
most of these drivers.  But we want to clean that up.  Call out the
include of module.h in the modular network drivers.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index a4eae75..f414ffb 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -14,6 +14,7 @@
  *
  */
 #include <linux/phy.h>
+#include <linux/module.h>
 
 #define RTL821x_PHYSR		0x11
 #define RTL821x_PHYSR_DUPLEX	0x2000