drm/xe: Get hwe domain specific FW to read RING_TIMESTAMP

Per client engine utilization uses RING_TIMESTAMP to return
drm-total-cycles to the user. Current code uses XE_FW_GT to read this
register on the first available engine in a GT. When testing on DG2, it
is observed that this value is 0 when running test on some engines. To
resolve that, get the hwe domain specific FW for reading the engine
timestamp.

v2:
- update commit message
- use domain specific FW (Matt)

v3:
- Drop check for hwe in the helper (Matt, Michal)

v4:
- checkpatch fixes

v5: Rebase

Fixes: 188ced1e

 ("drm/xe/client: Print runtime to fdinfo")
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240627235105.2631135-1-umesh.nerlige.ramappa@intel.com