sparc64: Fix asm/percpu.h build error

In order to break a header dependency between lockdep and task_struct,
I need per-cpu stuff from lockdep.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Link: https://lkml.kernel.org/r/20200623083721.277992771@infradead.org