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

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