serial: mxs-auart: use a function name to reflect what it really does

This function clears the reset the AUART unit is in after system start
to make it work.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>