staging: android: ion: fix ion_dma_buf_attach signatur

Fixup for "dma_buf: remove device parameter from attach callback v2".

I missed this driver, sorry for the noise. Patch is not even compile
tested.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/230641/