tty: serial: lpuart: Use defines that correspond to correct register

tty: serial: lpuart: Use defines that correspond to correct register

Use define from the 32-bit register description UARTMODIR_* instead of
UARTMODEM_*. The value is the same, so there is no functional change.

Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Reviewed-by: Stefan Agner <stefan.agner@toradex.com>
Reviewed-by: Fugang Duan <fugang.duan@nxp.com>
Link: https://lore.kernel.org/r/20191017141428.10330-2-philippe.schenker@toradex.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>