staging: fsl-dpaa2/eth: Only store bpid in priv struct

We only need to know the buffer pool id, so save exactly
that in the device's private structure, instead of the
entire DPBP attributes struct.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>