cpufreq: Fix warning on unused of_device_id tables for !CONFIG_OF

cpufreq: Fix warning on unused of_device_id tables for !CONFIG_OF

!CONFIG_OF builds cause warnings on unused of_device_id tables. This is
due to of_match_node() being a macro rather than static inline function.
Add a __maybe_unused annotation to the of_device_id tables.

Fixes: c7582ec85342 ("cpufreq: Drop CONFIG_ARM and CONFIG_ARM64 dependency on Arm drivers")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202408090714.wcrqU6Pk-lkp@intel.com/
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>