serial: fsl_lpuart: Fix earlycon support

Earlycon support for Freescale lpuart should only be enabled when
console support is enabled.

Fixes: 1d59b382 ("serial: fsl_lpuart: add earlycon support")
Acked-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>