drm/xe: Add xe_gt_clock_interval_to_ms helper

Add helper to convert GT clock ticks to msec. Useful for determining if
timeouts occur by examing GT clock ticks.

v6:
- s/nom/n , s/dom/d (Jonathan)
- include math64 (CI)

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240611144053.2805091-6-matthew.brost@intel.com