drm/xe: Add support for per-function engine activity

drm/xe: Add support for per-function engine activity

Add support for function level engine activity stats.
Engine activity stats are enabled when VF's are enabled

v2: remove unnecessary initialization
    move offset to improve code readability (Umesh)
    remove global for function engine activity (Lucas)

v3: fix commit message (Michal)

v4: remove enable function parameter
    fix kernel-doc (Umesh)

Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Riana Tauro <riana.tauro@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250311071759.2117211-2-riana.tauro@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>