MIPS: MSP71xx: Fix build error.

After the recent cleanup of the register_*_smp_ops() functions msp71xx
wasn't fixed to include the now necessary header resulting in:

/home/ralf/src/linux/upstream-linus/arch/mips/pmc-sierra/msp71xx/msp_setup.c: In function ‘prom_init’:
/home/ralf/src/linux/upstream-linus/arch/mips/pmc-sierra/msp71xx/msp_setup.c:231:2: error: implicit declaration of function ‘register_vsmp_smp_ops’ [-Werror=implicit-function-declaration]
cc1: all warnings being treated as errors
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/pmc-sierra/msp71xx/msp_setup.c

@@ -14,6 +14,7 @@
 #include <asm/cacheflush.h>
 #include <asm/r4kcache.h>
 #include <asm/reboot.h>
+#include <asm/smp-ops.h>
 #include <asm/time.h>
 
 #include <msp_prom.h>