staging: android: ion: Get rid of ion_sg_table

The ion_sg_table interface is mostly a reimplementation of
what dma_buf is doing. Clients should be using dma_buf APIs instead.

Signed-off-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>