drm/xe: Prevent runtime PM wake while reading rp0 frequency

drm/xe: Prevent runtime PM wake while reading rp0 frequency

The rp0 frequency is a fused value that is read once during probe
and then cached, so there’s no need to trigger a runtime wake
when accessing rp0.

Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Reviewed-by: Karthik Poosa <karthik.poosa@intel.com>
Link: https://lore.kernel.org/r/20251015094611.1468939-1-badal.nilawar@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>