VtsKernelProcFileApi: make CONFIG_CPU_FREQ_TIMES optional

These proc files are bound to CONFIG_CPU_FREQ_TIMES which is optional:
/proc/uid_time_in_state
/proc/uid_concurrent_active_time
/proc/uid_concurrent_policy_time

Fixes: 139099388
Test: vts-tradefed run commandAndExit vts-kernel
--skip-all-system-status-check --primary-abi-only --skip-preconditions
--skip-device-info --module VtsKernelProcFileApi
Change-Id: I72b2cb6d9d51f433e8f7e5eb68eb570e11fef0a0
Merged-In: I72b2cb6d9d51f433e8f7e5eb68eb570e11fef0a0
(cherry picked from commit f825b6ed8ee484e112e69b76eb6ae9e8571a40ce)