arm64: tegra: add node for tegra234 cpufreq

Adding cclpex node to represent Tegra234 cpufreq.
Tegra234 uses some of the CRAB (Control Register Access Bus)
registers for cpu frequency requests. These registers are
memory mapped to CCPLEX_MMCRAB_ARM region. In this node, mapping
the range of MMCRAB registers required only for cpu frequency info.

Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>