sun7i: Merge timer-code into plat-sunxi timer code

As a bonus this also adds a better sched_clock function for sun4i/sun5i.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
sun7i: Directly uses plat-sunxi devices.c

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
sun7i: Remove unused printk.c and sunxi_dump_reg.c files

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