drm/i915: move i915 specific bo implementation to i915
The bo interface implementation is different for both i915 and xe. Move
the i915 specific implementation from display to i915 core.
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/e159166d623899996a51a577365ca7ab9b1a0974.1773238670.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>