dpaa_eth: use big endian accessors

Ensure correct access to the big endian QMan HW through proper
accessors.

Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>