Add missing field to the list of fields to register.

Change-Id: I2590bf69f6778deb15f405c0976c9849af5b4a4e
Reviewed-on: https://code.wireshark.org/review/3685
Reviewed-by: Guy Harris <guy@alum.mit.edu>

epan/dissectors/packet-hpext.c

@@ -111,6 +111,7 @@ proto_register_hpext(void)
 {
 #ifndef HAVE_HFI_SECTION_INIT
 	static header_field_info *hfi[] = {
+		&hfi_hpext_reserved,
 		&hfi_hpext_dxsap,
 		&hfi_hpext_sxsap,
 	};