drm/xe/debugfs: Update xe_tuning_dump signature

drm/xe/debugfs: Update xe_tuning_dump signature

Our debugfs helper xe_gt_debugfs_show_with_rpm() expects print()
functions to return int. New signature allows us to drop wrapper.

While around, print additional separation lines using puts() to
avoid output with leading \n which might confuse some printers.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20250923211613.193347-4-michal.wajdeczko@intel.com