i915/guc: Accumulate active runtime on gt reset

On gt reset, if a context is running, then accumulate it's active time
into the busyness counter since there will be no chance for the context
to switch out and update it's run time.

v2: Move comment right above the if (John)

Fixes: 77cdd054 ("drm/i915/pmu: Connect engine busyness stats from GuC to pmu")
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241127174006.190128-4-umesh.nerlige.ramappa@intel.com