[PATCH v2 5/7] powerpc/85xx: Add MChk handler for SRIO port

[Bounine, Alexandre]

> I'm looking at this now and wondering what we added the mcheck handler
for in the first place and what
> its trying to accomplish.
> 
> - k

This protects system from hanging if RIO link fails or enters error
state. In some situations following maintenance read may initiate link
recovery from error state.

As it is now, MCheck mostly prevents system from hanging, but it also
adds sense to return status of maintenance read routine. I am using
return status in my new set of patches to check if RIO link is valid
during error recovery.

Alex.