xhci: dbctty: disable ECHO flag by default

JIRA: https://issues.redhat.com/browse/RHEL-116007

commit 2b857d6
Author: =?UTF-8?q?=C5=81ukasz=20Bartosik?= <ukaszb@chromium.org>
Date: Fri, 27 Jun 2025 17:41:21 +0300

  When /dev/ttyDBC0 device is created then by default ECHO flag
  is set for the terminal device. However if data arrives from
  a peer before application using /dev/ttyDBC0 applies its set
  of terminal flags then the arriving data will be echoed which
  might not be desired behavior.

  Fixes: 4521f16 ("xhci: dbctty: split dbc tty driver registration and unregistration functions.")
  Cc: stable <stable@kernel.org>
  Signed-off-by: Łukasz Bartosik <ukaszb@chromium.org>
  Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
  Link: https://lore.kernel.org/stable/20250610111802.18742-1-ukaszb%40chromium.org
  Link: https://lore.kernel.org/r/20250627144127.3889714-4-mathias.nyman@linux.intel.com
  Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Desnes Nunes <desnesn@redhat.com>

Author: Desnes Nunes

drivers/usb/host/xhci-dbgtty.c

@@ -617,6 +617,7 @@ int dbc_tty_init(void)
 	dbc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
 	dbc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
 	dbc_tty_driver->init_termios = tty_std_termios;
+	dbc_tty_driver->init_termios.c_lflag &= ~ECHO;
 	dbc_tty_driver->init_termios.c_cflag =
 			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
 	dbc_tty_driver->init_termios.c_ispeed = 9600;