x86: change size of node ids from u8 to s16

Change the size of node ids for X86_64 from u8 to s16 to
accomodate more than 32k nodes and allow for NUMA_NO_NODE
(-1) to be sign extended to int.

Cc: David Rientjes <rientjes@google.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>