drm/xe: enable idle msg and set hysteresis for GSCCS

drm/xe: enable idle msg and set hysteresis for GSCCS

On MTL (and only on MTL) the GSCCS defaults with idle messaging
disabled. This means that, once awoken, the GSCCS will never signal its
idleness to the GT. To allow the GT to enter the proper low-power state,
we need therefore to turn idle messaging on. As part of this, we also
need to set a proper hysteresis value for the engine.

v2: use MEDIA_VERSION() and CLR() for the RTP rule and action, add reg
bit define in descending order (Matt)

Bspec: 71496
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230817221707.1602873-1-daniele.ceraolospurio@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>