Added and improved several prints related to the GDB connection and various error states that may occur in relation to this connection. Change-Id: I233246190b613cc925b783561cfa3aa5267360fd Signed-off-by: Jan Matyas <matyas@codasip.com> Reviewed-on: https://review.openocd.org/c/openocd/+/6288 Reviewed-by: Tim Newsome <tim@sifive.com> Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com> Tested-by: jenkins