server: gdb: export gdb_actual_connections through a function

The internal variable 'gdb_actual_connections' is used by log and
by semihosting to determine if there are active GDB connections.

Keep the variable local in server's code and only export its value
through a dedicated function.

This solves the issue detected by 'parse' of the variable defined
as global but not declared in any include file.

Change-Id: I6e14f4cb1097787404094636f8a2a291340222dd
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7673
Tested-by: jenkins

src/server/gdb_server.c

@@ -117,7 +117,7 @@ static void gdb_sig_halted(struct connection *connection);
 
 /* number of gdb connections, mainly to suppress gdb related debugging spam
  * in helper/log.c when no gdb connections are actually active */
-int gdb_actual_connections;
+static int gdb_actual_connections;
 
 /* set if we are sending a memory map to gdb
  * via qXfer:memory-map:read packet */
@@ -4105,3 +4105,8 @@ void gdb_service_free(void)
 	free(gdb_port);
 	free(gdb_port_next);
 }
+
+int gdb_get_actual_connections(void)
+{
+	return gdb_actual_connections;
+}