Merge branch 'dpaa_eth-buffer-layout-fixes'

Merge branch 'dpaa_eth-buffer-layout-fixes'

Camelia Groza says:

====================
dpaa_eth: buffer layout fixes

The patches are related to the software workaround for the A050385 erratum.
The first patch ensures optimal buffer usage for non-erratum scenarios. The
second patch fixes a currently inconsequential discrepancy between the
FMan and Ethernet drivers.

Changes in v3:
- refactor defines for clarity in 1/2
- add more details on the user impact in 1/2
- remove unnecessary inline identifier in 2/2

Changes in v2:
- make the returned value for TX ports explicit in 2/2
- simplify the buf_layout reference in 2/2
====================

Link: https://lore.kernel.org/r/cover.1604339942.git.camelia.groza@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>