drm/i915: move page_sizes to runtime info

If it's modified runtime, it's runtime info.

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/f6825dd97d2ba63aa395c30131c4b9e6ef32b0c8.1660910433.git.jani.nikula@intel.com