drm/i915/pmu: Avoid with_intel_runtime_pm within spinlock

When guc timestamp ping worker runs it takes the spinlock and calls
with_intel_runtime_pm.  Since with_intel_runtime_pm may sleep, move the
spinlock inside __update_guc_busyness_stats.

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211120014201.26480-1-umesh.nerlige.ramappa@intel.com