MIPS: OCTEON: Add SMP support for OCTEON cn78xx et al.

OCTEON chips with the CIU3 interrupt controller use a different IPI
mechanism that previous models.

Add plat_smp_ops for the cn78xx and probing code to choose between the
two types of ops.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12499/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/octeon/octeon.h

@@ -299,6 +299,12 @@ static inline void octeon_npi_write32(uint64_t address, uint32_t val)
 	cvmx_read64_uint32(address ^ 4);
 }
 
+#ifdef CONFIG_SMP
+void octeon_setup_smp(void);
+#else
+static inline void octeon_setup_smp(void) {}
+#endif
+
 struct irq_domain;
 struct device_node;
 struct irq_data;