[parisc-linux] NFS root fixed (I believe)

[John Marvin]

I just checked in changes that I believe fix nfs root. It turns out
that the in_interrupt() macro was not working, probably due to a
2.4 merge mistake. Anyway, since it wasn't working, schedule() was
being called under interrupt. And since schedule calls in_interrupt()
to check for that possibility, it was not catching it, therefore it
was switching contexts under interrupt, trashing kernel stacks, etc.

John