hv: remove free_channel() from hyperv.h

This function is only used in the file it is declared in
(channel_mgmt.c) so make it static and remove it from the hyperv.h file.

Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index a2fc487..12b85ff 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -196,7 +196,7 @@
 /*
  * free_channel - Release the resources used by the vmbus channel object
  */
-void free_channel(struct vmbus_channel *channel)
+static void free_channel(struct vmbus_channel *channel)
 {
 
 	/*