cpufreq: intel_pstate: Fix code ordering in intel_pstate_set_policy()

The limits->max_perf is rounded_up but immediately overwritten by
another assignment to limits->max_perf.

Move that operation to the correct location.

While here also added a pr_debug() call in ->set_policy to aid in
debugging.

Fixes: 785ee278 (cpufreq: intel_pstate: Fix limits->max_perf rounding error)
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw : Subject & changelog ]
Cc: 4.4+ <stable@vger.kernel.org> # 4.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>