tty: serial: fsl_lpuart: add polled console functions

This adds polling functions as used by kgdb.

Signed-off-by: Nicolae Rosia <nicolae_rosia@mentor.com>
Signed-off-by: Stefan Golinschi <stefan.golinschi@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>