linux-phytec-fsl

serial: imx: Allow module build

There is no need to only allow the serial driver to be built-in.

Allow the imx serial driver to be built as a module.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>