tty/serial: atmel: remove unneeded atmel_get_lines_status function

tty/serial: atmel: remove unneeded atmel_get_lines_status function

Since commit 18dfef9c7f87 ("serial: atmel: convert to irq handling
provided mctrl-gpio"), the GPIOs interrupts are handled by
mctrl_gpio_irq_handle().
So, atmel_get_lines_status() can be completely killed and replaced by :
atmel_uart_readl(port, ATMEL_US_CSR);

Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Link: https://lore.kernel.org/r/20190826071752.30396-1-richard.genoud@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>