[U-Boot] DCache in designware.c brakes bf609-ezkit board build

[Vasili Galka]

Hi Alexey,

Your commit 50b0df814b0f75c08a3d45a017016a75af3edb5d caused
drivers/net/designware.c to be dependent on dcache functionality, e.g.
invalidate_dcache_range(). This brakes build for configurations that don't
have this implemented. For example the blackfin based "bf609-ezkit" board
does
not build now since it uses designware.c but there is no dcache related
stuff
for the blackfin arch.

What do you see as the right solution for this? Implement some stub
functions
for dcache on blackfin? #ifdef the dcache calls in designware.c? If the
later, what CONFIG conditions are the best to use?

Looking forward for your opinion.

Best,
Vasili