serial: mxs-auart: Remove unneeded platform_device_id

The mxs-auart driver is only used for DT platforms and there is no
need to use the platform_device_id structure.

Get rid the platform_device_id structure and retrieve the data via
of_device_get_match_data(), which simplifies the code.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20201123190438.5636-1-festevam@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>