serial: fsl_lpuart: Remove unneeded OOM error message

There is no need to add an out-of-memory error message inside
the driver because the core MM code will take care of it.

Remove the unneeded OOM error message.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>