This patch replaces the open_pic IRQ controller driver with a new
version rewritten from scratch, called "mpic" (this is the name of
IBM's open_pic implementation and also the only one actually used
on any platform).

It is smaller, hopefully more readable, supports the various variants
of the cell in a single driver (open_pic_u3.c is gone), and adds
optional support for the workaround of U3 mpic beeing used along with
IO-APICs on HyperTransport (the eval board will uses that, among
others).
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>