Drivers: hv: vmbus: add a helper function to set a channel's pending send size

BugLink: http://bugs.launchpad.net/bugs/1541585

This will be used by the coming net/hvsock driver.
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 3c75354d)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

include/linux/hyperv.h

@@ -816,6 +816,12 @@ static inline void *get_per_channel_state(struct vmbus_channel *c)
 	return c->per_channel_state;
 }
 
+static inline void set_channel_pending_send_size(struct vmbus_channel *c,
+						 u32 size)
+{
+	c->outbound.ring_buffer->pending_send_sz = size;
+}
+
 void vmbus_onmessage(void *context);
 
 int vmbus_request_offers(void);