Do not abort DC refill

[wallento]

Hi,

with this commit it was introduced that the DC refill aborts on snoop hits: https://github.com/openrisc/mor1kx/commit/87283e96a14ebfe8b6686ded5e2cc68ac6fce8b5

The issue is that the wishbone spec does not allow to just abort a transaction and I had a chain of events to led to a crash eventually.

@skristiansson fortunately documented the change very well, thanks!

I am wondering if a solution based on the outline in the commit or a solution where the bus itnerface unit completes a burst after two words and then withdraws the data is better.

What do you think?

Cheers, Stefan