tools/power/turbostat: Relocate cstate probing code

Move all cstate probing related code into probe_cstates().

Note that dump_platform_info() actually dumps both MSR_PLATFORM_INFO and
MSR_IA32_POWER_CTL. MSR_PLATFORM_INFO is for pstate and
MSR_IA32_POWER_CTL is for cstate. So split dump_platform_info() and dump
MSR_IA32_POWER_CTL in probe_cstates().

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>