tty: serial: lpc32xx_hs: don't call tty_flip_buffer_push() twice

serial_lpc32xx_interrupt() calls __serial_lpc32xx_rx() first and then
tty_flip_buffer_push() immediately after that. But last statement of
__serial_lpc32xx_rx() already called tty_flip_buffer_push()..

So, probably its not required to be called twice. Lets remove one of them.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>