drm/xe: Donot apply forcewake while reading actual frequency

RPSTAT1 is an sgunit register and thus doesn't need forcewake.
MTL_MIRROR_TARGET_WP1 is within an "always on" power domain and thus
doesn't require any forcewake to ensure the register is powered
up and usable. When GT is RC6 the actual frequency reported will be 0.

v2:
 - Add bspec index (Anshuman)
 - %s/GEN12_RPSTAT1/GT_PERF_STATUS as per bspec
v3: Update Fixes tag

Bspec: 51837, 67651
Fixes: dd08ebf6 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230609024954.987039-1-badal.nilawar@intel.com


Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>