Staging: hv: make some vmbus_drv functions static

Now that vmbus_drv.c is merged with vmbus.c, some of the newly global
functions can now be marked static.

Cc: Haiyang Zhang <[e-mail]>
Cc: Hank Janssen <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/hv/vmbus_api.h

···
 	void *Extension;
 };
 
-int vmbus_on_isr(struct hv_driver *drv);
-void vmbus_on_msg_dpc(struct hv_driver *drv);
-void vmbus_on_event_dpc(struct hv_driver *drv);
-
 #endif /* _VMBUS_API_H_ */

drivers/staging/hv/vmbus_drv.c

···
 /*
  * vmbus_on_msg_dpc - DPC routine to handle messages from the hypervisior
  */
-void vmbus_on_msg_dpc(struct hv_driver *drv)
+static void vmbus_on_msg_dpc(struct hv_driver *drv)
 {
 	int cpu = smp_processor_id();
 	void *page_addr = hv_context.synic_message_page[cpu];
···
 /*
  * vmbus_on_event_dpc - DPC routine to handle events from the hypervisior
  */
-void vmbus_on_event_dpc(struct hv_driver *drv)
+static void vmbus_on_event_dpc(struct hv_driver *drv)
 {
 	/* TODO: Process any events */
 	VmbusOnEvents();
···
 /*
  * vmbus_on_isr - ISR routine
  */
-int vmbus_on_isr(struct hv_driver *drv)
+static int vmbus_on_isr(struct hv_driver *drv)
 {
 	int ret = 0;
 	int cpu = smp_processor_id();