Instead of modifying the device info on the fly, use static const mock
device info.

It's not okay to modify device info at runtime; we've added separate
runtime info for info that needs to be modified at runtime. We've added
safeguards to device info to prevent it from being modified, but commit
5e352e32 ("drm/i915: preparation for using PAT index") just cast the
const away and modified it anyway. This prevents device info from being
moved to rodata.

Fixes: 5e352e32 ("drm/i915: preparation for using PAT index")
Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b0db62045a96a3fd4cf123685da88cc777f9b485.1687878757.git.jani.nikula@intel.com