drm/xe/gsc: Turn off GSCCS interrupts when disabling the engine

Starting on LNL, there is a new GSCCS interrupt that is triggered when
the GSC engine reset fails. If the HW is in a bad state, this interrupt
might end up being triggered even if we're not using the engine, which
will lead to a warning because we'll see it as unexpected. Since there
is no point in handling the interrupt in this scenario, we can just
make sure the interrupts are off when we disable the engine.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Tested-by: Matt Roper <matthew.d.roper@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/20240419183412.1605782-1-daniele.ceraolospurio@intel.com