blackfin: SMP: pda: "next" field of blackfin_pda only used in SMP kernel

Signed-off-by: Steven Miao <realmz6@gmail.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>

arch/blackfin/include/asm/pda.h

@@ -13,7 +13,9 @@
 #ifndef __ASSEMBLY__
 
 struct blackfin_pda {			/* Per-processor Data Area */
+#ifdef CONFIG_SMP
 	struct blackfin_pda *next;
+#endif
 
 	unsigned long syscfg;
 #ifdef CONFIG_SMP