tty: serial: fsl_lpuart: drop EARLYCON_DECLARE

EARLYCON_DECLARE is just a wrapper of OF_EARLYCON_DECLARE,
since we already have OF_EARLYCON_DECLARE for lpuart and lpuart32,
so no need EARLYCON_DECLARE.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/1576822230-23125-2-git-send-email-peng.fan@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>