powerpc/cell: Fix crash in iic_setup_cpu() after per_cpu changes

The conversion from __get_cpu_var() to this_cpu_ptr() in iic_setup_cpu()
is wrong. It causes an oops at boot.

We need the per-cpu address of struct cpu_iic, not cpu_iic.regs->prio.

Sparse noticed this, because we pass a non-iomem pointer to out_be64(),
but we obviously don't check the sparse results often enough.

Fixes: 69111bac ("powerpc: Replace __get_cpu_var uses")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>