rockchip: rk3368: remove setup of secure timer from TPL/SPL

When using DM timers w/ the timer0 block within the RK3368, we no
longer depend on the ARMv8 generic timer counting.  This allows us to
drop the secure timer initialisation from the TPL and SPL stages.

The secure timer will later be set up by ATF, which starts the ARMv8
generic timer.  Thus, there will be a dependency from Linux to the ATF
through the ARMv8 generic timer... this seems reasonable, as Linux
will require the ATF (and PSCI) to start up the secondary cores anyway
(in other words: we don't add any new dependencies).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>