cpufreq: intel_pstate: Fix cpuinfo_max_freq when MSR_TURBO_RATIO_LIMIT is 0

The MSR_TURBO_RATIO_LIMIT can be 0. This is not an error. User can update
this MSR via BIOS settings on some systems or can use msr tools to update.
Also some systems boot with value = 0.

This results in display of cpufreq/cpuinfo_max_freq wrong. This value
will be equal to cpufreq/base_frequency, even though turbo is enabled.

But platform will still function normally in HWP mode as we get max
1-core frequency from the MSR_HWP_CAPABILITIES. This MSR is already used
to calculate cpu->pstate.turbo_freq, which is used for to set
policy->cpuinfo.max_freq. But some other places cpu->pstate.turbo_pstate
is used. For example to set policy->max.

To fix this, also update cpu->pstate.turbo_pstate when updating
cpu->pstate.turbo_freq.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>