sparc64: Fix build regression

This patch fixes build error which was introduced by commit

812cb83a (Implement HAVE_CONTEXT_TRACKING).

[*]https://lkml.org/lkml/2013/11/23/103



Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
CC: David Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>