hv: fix 'User name starts with underscore'

There are chances that names with leading underscore declared by
developers are conflict with the ones reserved for the compiler.

What this patch does:
- rename these functions/variables/macros starting with
  underscore to avoid such unintentational mistakes.
- remove gpr.h without any contents

Tracked-On: #861
Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/include/arch/x86/guest/vm.h

@@ -146,13 +146,6 @@ struct vm {
 				     * when vm is active. So no lock needed
 				     */
 
-	struct _vm_shared_memory *shared_memory_area;
-
-	struct {
-		struct _vm_virtual_device_node *head;
-		struct _vm_virtual_device_node *tail;
-	} virtual_device_list;
-
 	unsigned char GUID[16];
 	struct secure_world_control sworld_control;