tty: serial: lpc32xx_hs: Remove unused variable 'tmp'

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

 drivers/tty/serial/lpc32xx_hs.c: In function ‘__serial_uart_flush’:
 drivers/tty/serial/lpc32xx_hs.c:244:6: warning: variable ‘tmp’ set but not used [-Wunused-but-set-variable]

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: Sylvain Lemieux <slemieux.tyco@gmail.com>
Cc: Kevin Wells <kevin.wells@nxp.com>
Cc: Roland Stigge <stigge@antcom.de>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Vladimir Zapolskiy <vz@mleia.com>
Link: https://lore.kernel.org/r/20201104193549.4026187-20-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/lpc32xx_hs.c

@@ -241,12 +241,11 @@ static unsigned int __serial_get_clock_div(unsigned long uartclk,
 
 static void __serial_uart_flush(struct uart_port *port)
 {
-	u32 tmp;
 	int cnt = 0;
 
 	while ((readl(LPC32XX_HSUART_LEVEL(port->membase)) > 0) &&
 	       (cnt++ < FIFO_READ_LIMIT))
-		tmp = readl(LPC32XX_HSUART_FIFO(port->membase));
+		readl(LPC32XX_HSUART_FIFO(port->membase));
 }
 
 static void __serial_lpc32xx_rx(struct uart_port *port)