powerpc/pseries: Add and use LPPACA_SIZE constant

Helps document what the hard-coded number means.

Also take the opportunity to fix an #endif comment.
Suggested-by: Alexey Kardashevskiy <aik@linux.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190820021326.6884-8-bauerman@linux.ibm.com

arch/powerpc/kernel/paca.c

@@ -52,6 +52,8 @@ static void *__init alloc_paca_data(unsigned long size, unsigned long align,
 
 #ifdef CONFIG_PPC_PSERIES
 
+#define LPPACA_SIZE 0x400
+
 /*
  * See asm/lppaca.h for more detail.
  *
@@ -65,7 +67,7 @@ static inline void init_lppaca(struct lppaca *lppaca)
 
 	*lppaca = (struct lppaca) {
 		.desc = cpu_to_be32(0xd397d781),	/* "LpPa" */
-		.size = cpu_to_be16(0x400),
+		.size = cpu_to_be16(LPPACA_SIZE),
 		.fpregs_in_use = 1,
 		.slb_count = cpu_to_be16(64),
 		.vmxregs_in_use = 0,
@@ -75,19 +77,18 @@ static inline void init_lppaca(struct lppaca *lppaca)
 static struct lppaca * __init new_lppaca(int cpu, unsigned long limit)
 {
 	struct lppaca *lp;
-	size_t size = 0x400;
 
-	BUILD_BUG_ON(size < sizeof(struct lppaca));
+	BUILD_BUG_ON(sizeof(struct lppaca) > LPPACA_SIZE);
 
 	if (early_cpu_has_feature(CPU_FTR_HVMODE))
 		return NULL;
 
-	lp = alloc_paca_data(size, 0x400, limit, cpu);
+	lp = alloc_paca_data(LPPACA_SIZE, 0x400, limit, cpu);
 	init_lppaca(lp);
 
 	return lp;
 }
-#endif /* CONFIG_PPC_BOOK3S */
+#endif /* CONFIG_PPC_PSERIES */
 
 #ifdef CONFIG_PPC_BOOK3S_64