x86: vdso: Put declaration before code

Sigh, warnings are there for a reason.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: John Stultz <john.stultz@linaro.org>

arch/x86/kernel/vsyscall_64.c

@@ -83,9 +83,10 @@ void update_vsyscall_tz(void)
 void update_vsyscall(struct timespec *wall_time, struct timespec *wtm,
 			struct clocksource *clock, u32 mult)
 {
-	write_seqcount_begin(&vsyscall_gtod_data.seq);
 	struct timespec monotonic;
 
+	write_seqcount_begin(&vsyscall_gtod_data.seq);
+
 	/* copy vsyscall data */
 	vsyscall_gtod_data.clock.vclock_mode	= clock->archdata.vclock_mode;
 	vsyscall_gtod_data.clock.cycle_last	= clock->cycle_last;