soc: fsl: dpio: Add prefetch instruction

In dpaa2_io_store_next(), if the current dequeue entry is not
the last, prefetch the next one as most likely it will be
requested shortly by the consumer driver.

This brings a ~3% improvement for dpaa2 ethernet driver
IP forwarding with small size frames.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>