iris: finish aux import on get_param

A buffer and its aux are imported separately, if the aux import is
not completed yet when resource_get_param is called, merge the
separate aux a.k.a the 2nd image into the main image.

Fixes: 246eebba ("iris: Export and import surfaces with modifiers that have aux data")

Signed-off-by: James Xiong <james.xiong@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
(cherry picked from commit fd235484)