hv: hyperv.h: remove unneeded forward declarations of structures

This file was created by mushing different .h files together and it
shows.  This change removes some unneeded forward declarations.

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

include/linux/hyperv.h

@@ -693,9 +693,6 @@ extern void vmbus_get_debug_info(struct vmbus_channel *channel,
 
 extern void vmbus_ontimer(unsigned long data);
 
-struct hv_driver;
-struct hv_device;
-
 struct hv_dev_port_info {
 	u32 int_mask;
 	u32 read_idx;