tty: serial: jsm: jsm_cls: Remove unused variable 'discard'

tty: serial: jsm: jsm_cls: Remove unused variable 'discard'

Fixes the following W=1 kernel build warning(s):

 drivers/tty/serial/jsm/jsm_cls.c: In function ‘cls_copy_data_from_uart_to_queue’:
 drivers/tty/serial/jsm/jsm_cls.c:400:7: warning: variable ‘discard’ set but not used [-Wunused-but-set-variable]

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-12-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>