powerpc: Enable flush and invalidate dcache by range for MPC85xx

powerpc: Enable flush and invalidate dcache by range for MPC85xx

Commit ac337168a unified functions to flush and invalidate dcache by
range. These two functions were no-ops for SoCs other than 4xx and
MPC86xx. Adding these functions seemed to be correct but introduced
issues in some drivers when the dcache was flushed. While the root
cause was under investigation, these functions were disabled in
Commit cb1629f91a for affected SoCs, including the MPC85xx, to make
the various drivers work.

On the T208x USB stopped working after v2016.07 was pulled.  After
re-enabling the dcache functions for the MPC85xx it started working
again.  The USB and DPPA Ethernet drivers have been seen as
operational after this change but other drivers cannot be tested.

Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Tony O'Brien <tony.obrien@alliedtelesis.co.nz>
Cc: Marek Vasut <marex@denx.de>
Cc: York Sun <york.sun@nxp.com>
Reviewed-by: York Sun <york.sun>