staging: android: ion: Remove unnused function ion_handle_buffer

Remove the function ion_handle_buffer since it is not used anywhere.

Signed-off-by: Johanna Abrahamsson <johanna@mjao.org>
Acked-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>