use BUILD_BUG_ON in FPU code

From: Alexey Dobriyan <adobriyan@gmail.com>

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 arch/x86_64/kernel/i387.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

Index: linux/arch/x86_64/kernel/i387.c
===================================================================
--- linux.orig/arch/x86_64/kernel/i387.c
+++ linux/arch/x86_64/kernel/i387.c
@@ -82,11 +82,8 @@ int save_i387(struct _fpstate __user *bu
 	struct task_struct *tsk = current;
 	int err = 0;
 
-	{ 
-		extern void bad_user_i387_struct(void); 
-		if (sizeof(struct user_i387_struct) != sizeof(tsk->thread.i387.fxsave))
-			bad_user_i387_struct();
-	} 
+	BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
+			sizeof(tsk->thread.i387.fxsave));
 
 	if ((unsigned long)buf % 16) 
 		printk("save_i387: bad fpstate %p\n",buf);