MIPS: smp-mt: Fix link error when PROC_FS=n

Commit d6d3c9afaa (MIPS: MT: proc: Add support for printing VPE and TC
ids) causes a link error when CONFIG_PROC_FS=n:

arch/mips/built-in.o: In function `proc_cpuinfo_notifier_init':
smp-mt.c: undefined reference to `register_proc_cpuinfo_notifier'

This is fixed by adding an ifdef around the procfs handling code
in smp-mt.c.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reported-by: Markos Chandras <markos.chandras@imgtec.com>
Reviewed-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # >= 3.15
Patchwork: https://patchwork.linux-mips.org/patch/7244/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/smp-mt.c

@@ -288,6 +288,7 @@ struct plat_smp_ops vsmp_smp_ops = {
 	.prepare_cpus		= vsmp_prepare_cpus,
 };
 
+#ifdef CONFIG_PROC_FS
 static int proc_cpuinfo_chain_call(struct notifier_block *nfb,
 	unsigned long action_unused, void *data)
 {
@@ -309,3 +310,4 @@ static int __init proc_cpuinfo_notifier_init(void)
 }
 
 subsys_initcall(proc_cpuinfo_notifier_init);
+#endif