serial: uartlite: Fix BRKINT clearing

BRKINT is within c_iflag rather than c_cflag.

Fixes: ea017f58 (tty: serial: uartlite: Prevent changing fixed parameters)
Reviewed-by: Sean Anderson <sean.anderson@seco.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220519081808.3776-2-ilpo.jarvinen@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>