drm/xe: Convert hwmon from mem_access to xe_pm_runtime calls

Continue the work to kill the mem_access in favor of a pure runtime pm.

Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240222163937.138342-9-rodrigo.vivi@intel.com