Drivers: hv: Make the vmbus driver unloadable

It turns out that the vmbus driver can be made unloadable. Make it
unloadable.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/hv/hv.c

@@ -237,6 +237,9 @@ void hv_cleanup(void)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 
+	/* Reset our OS id */
+	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
+
 	kfree(hv_context.signal_event_buffer);
 	hv_context.signal_event_buffer = NULL;
 	hv_context.signal_event_param = NULL;