uboot-imx

ARM64: zynqmp: Setup correct COUNTER_FREQUENCY for silicon

When U-Boot runs from EL3 system timer is setup based on this macro.
Software default freq for silicon is 100MHz but enable opton to rewrite
it. Emulation platform is using 4MHz.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>