powerpc/64s/radix: Fix CONFIG_SMP=n build

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200302010410.2957362-1-npiggin@gmail.com
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index dd1bea4..2a9a0cd 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -26,6 +26,7 @@
 #include <asm/firmware.h>
 #include <asm/powernv.h>
 #include <asm/sections.h>
+#include <asm/smp.h>
 #include <asm/trace.h>
 #include <asm/uaccess.h>
 #include <asm/ultravisor.h>