x86-64: Remove vsyscall number 3 (venosys)

It just segfaults since April 2008 (a4928cff), so I'm pretty
sure that nothing uses it. And having an empty section makes
the linker script a bit fragile.

Signed-off-by: Andy Lutomirski <[e-mail]>
Cc: Jesper Juhl <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Arjan van de Ven <[e-mail]>
Cc: Jan Beulich <[e-mail]>
Cc: richard -rw- weinberger <[e-mail]>
Cc: Mikael Pettersson <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Louis Rilling <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/kernel/vmlinux.lds.S

···
 		*(.vsyscall_2)
 	}
 
-	.vsyscall_3 ADDR(.vsyscall_0) + 3072: AT(VLOAD(.vsyscall_3)) {
-		*(.vsyscall_3)
-	}
-
 	. = ALIGN(__vsyscall_0 + PAGE_SIZE, PAGE_SIZE);
 
 #undef VSYSCALL_ADDR

arch/x86/kernel/vsyscall_64.c

···
 	return 0;
 }
 
-static long __vsyscall(3) venosys_1(void)
-{
-	return -ENOSYS;
-}
-
 /* Assume __initcall executes before all user space. Hopefully kmod
    doesn't violate that. We'll find out if it does. */
 static void __cpuinit vsyscall_set_cpu(int cpu)