mx6: remove imx6q_clock_map_io() since it does nothing

Since i.MX6 is a DT-"pure" platform it doesn't need any mappings,
as evidenced by the function being an empty, do-nothing stub. Rather
than keeping it around, get rid of it..
preempt: fix from upstream

We'd never notice because we enabled PREEMPT..

Patrik Kluba <pkluba@dension.com>
arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n