iris: export GEM handle with RDWR access rights
There is a regression that made it impossible to export gem handles with write access. That is, a client may export gem handles of each buffer plane, then export dmabuf fds using these handles, and mmap these dmabuf in a different process (this is what Chromium does). After mesa/mesa!4861 , it became impossible as mmap resulted in EACCESS error as slightly different approach was taken for exporting these gem handles. This CL fixes exporting gem handles (which are exported from dmabuf fds) by adding the DRM_RDWR flag. Cc: mesa-stable Fixes #3119 Reviewed-by:Lionel Landwerlin <lionel.g.landwerlin@intel.com> Part-of: <mesa/mesa!10851>