sunxi-cpu-freq: Unify sun4i and sun5i code

Note if you do a diff between the 2, there are some differences, where as
this patch just moves the mach-sun4i code to plat-sunxi. The reason for this
is that the sun5i code does the same as the sun4i code just in a more
complicated manner.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>