drm/i915/hdcp: Pin the hdcp gsc message high in ggtt

drm/i915/hdcp: Pin the hdcp gsc message high in ggtt

AFAICS there is no hardware restriction on where in ggtt
the hdcp gsc message object needs to be bound. And as it's
a regular shmem object we don't need it be in the mappabe
range either. So pin it high to make avoid needlessly
wasting the precious mappable range for it.

Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231215110933.9188-3-ville.syrjala@linux.intel.com
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>