drm/i915: add initial runtime info into device info

Add initial runtime info that we can copy to runtime info at i915
creation time. This lets us define the initial values for runtime info
statically while making it possible to change them runtime. This will be
the new home for the current "const" device info members that are
modified runtime anyway.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Maarten Lankhort <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a77c6db2da20d401f47a0a5e87356b9b3f6292df.1660910433.git.jani.nikula@intel.com