m68k: coldfire/clk.c: move m5441x specific code

Moving specific m5441x clk-related code in more appropriate location,
since breaking compilation for other targets.

Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>
Link: https://lore.kernel.org/r/20200525102324.2723438-1-angelo.dureghello@timesys.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>