vmnet: use void as argument list in function definitions (#188)

Two functions use "foo()" rather than proper "foo(void)" in their
definitions and as reported, clang compiler treats it as an error.

While at it, also mark VNetFreeInterfaceList() static to make its
definition match the declaration.

vmnet-only/driver.c

@@ -1407,8 +1407,8 @@ VNetCycleDetectIf(const char *name, // IN:
  *----------------------------------------------------------------------
  */
 
-void
-VNetFreeInterfaceList()
+static void
+VNetFreeInterfaceList(void)
 {
    while (vnetInterfaces != NULL) {
       VNetInterface *next = vnetInterfaces->next;

vmnet-only/smac_compat.c

@@ -83,7 +83,7 @@
  */
 
 unsigned long SMACINT
-SMACL_GetUptime()
+SMACL_GetUptime(void)
 {
    return jiffies;
 }