Remove sparc64_multi_core because it's not used any more.

It was added by a2f9f6bb ("Fix {mc,smt}_capable()"), and the last uses
were removed by e637d96bf462 ("sched: Remove unused mc_capable() and
smt_capable()").
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: David S. Miller <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20140304210744.16893.75929.stgit@bhelgaas-glaptop.roam.corp.google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>