This patch increases some hardcoded limits people have already run into or
plan to go towards eventually.

Increase max MP busses on x86-64.  Needed for some machines.  Suggested by
Andrew Chen and James Cleverdon.

MAX_IRQ_SOURCES kept at 256 for now, matching i386.

Increase MAX_IO_APICS to 32 following i386.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>