x86_64 SGI UV: Fix writes to led registers on remote uv hubs.

The wrong address was being used to write the SCIR led regs on remote
hubs.  Also, there was an inconsistency between how BIOS and the kernel
indexed these regs.  Standardize on using the lower 6 bits of the APIC
ID as the index.

This patch fixes the problem of writing to an errant address to a
cpu # >= 64.

Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Jack Steiner <steiner@sgi.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>