rockchip: spl: RK3399: add COUNTER_FREQUENCY define to rk3399_common.h

rockchip: spl: RK3399: add COUNTER_FREQUENCY define to rk3399_common.h

The BootROM of the RK3399 SoC does not initialise the cntfrq_el0 (which
holds the value 0 (zero) on entry into the SPL. This causes the timebase
for U-Boot not to advance (and will cause a hang where a timeout would
be expected... e.g. if something goes wrong during MMC/SD card startup).

This change defines COUNTER_FREQUENCY, which is used by the AArch64 init
code in arch/arm/cpu/armv8/start.S to set up cntfrq_el0 (if necessary).

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