x86, UV: Correct BAU discovery of hubs and sockets

Correct the initialization-time assumption of contigous blade
numbers and of sockets numbered from zero.

There may be hubs present with no cpu's enabled.
There may be disabled sockets such that the active socket is not
number zero.

And assign a 'socket master' by assuming that a socket is a
node. (it is not safe to extract socket number from an apicid)

Signed-off-by: Cliff Wickman <cpw@sgi.com>
Cc: gregkh@suse.de
LKML-Reference: <E1OJvNy-0004aW-9S@eag09.americas.sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>