[PATCH 3/3] 8250: add workaround for MPC8[356]xx UART break IRQ storm

[Alan Cox]

> > OK, I'll simply change the above to CONFIG_PPC then.
> 
> It does, the bug is in the uart IP which I don't think we ever plan on fixing, so 32 or 64-bit parts will have it for ever and ever ;)

It should be runtime selected, there should be no ifdefs here.