percpu: add dummy pcpu_lpage_remapped() for !CONFIG_SMP

!CONFIG_SMP was missing pcpu_lpage_remapped() definition causing build
failure.  Add dummy implementation.  This was discovered by linux-next
testing.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>

include/linux/percpu.h

@@ -184,6 +184,11 @@ static inline void free_percpu(void *p)
 
 static inline void __init setup_per_cpu_areas(void) { }
 
+static inline void *pcpu_lpage_remapped(void *kaddr)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_SMP */
 
 #define alloc_percpu(type)	(type *)__alloc_percpu(sizeof(type), \