staging: fsl-dpaa2/eth: Reset dpbp

Reset the buffer pool object before using it, like we do
for the other DPAA2 objects.

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