HCrt fix no previous prototype for 'proto_register_hcrt' [-Wmissing-prototypes]

Change-Id: Idca780885263c068ba31bbccb6009e75221b3adf
Reviewed-on: https://code.wireshark.org/review/6816
Reviewed-by: Anders Broman <a.broman58@gmail.com>

epan/dissectors/packet-hcrt.c

@@ -60,6 +60,7 @@ static gint ett_hcrt_body = -1;
 static expert_field ei_hcrt_error = EI_INIT;
 
 void proto_reg_handoff_hcrt(void);
+void proto_register_hcrt(void);
 
 #define HCRT_HDR_LEN 4