[PATCH] x86: increase MAX_MP_BUSSES on default arch

Vitezslav Samel <samel@mail.cz> reports that an HP DL380 g4 fails using the
default arch due to the ISA bus having an ID of 32.

It would have worked OK with the generic arch - for some reason the default
arch doesn't support as many busses.

So bump that up to support 256 busses, but leave it at 32 if we're building a
tiny system to save a bit of memory.

Cc: Vitezslav Samel <samel@mail.cz>
Acked-by: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>