MIPS: SMTC: Fix build.

Commit ee6114202e48dc282c6d04741e9c5d7171eb8bb8 (lmo) rsp.
1685f3b1 (kernel.org) ["MIPS: SMTC: Move
declaration of smtc_init_secondary to <asm/smtc.h>."] didn't quite do
that - it rather lost the declaration of smtc_init_secondary resulting in
a build error.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/smtc.h

@@ -46,6 +46,7 @@ extern void smtc_prepare_cpus(int cpus);
 extern void smtc_smp_finish(void);
 extern void smtc_boot_secondary(int cpu, struct task_struct *t);
 extern void smtc_cpus_done(void);
+extern void smtc_init_secondary(void);
 
 
 /*