lguest: fix irq vectors.

	do_IRQ: cannot handle IRQ -1 vector 0x20 cpu 0
	------------[ cut here ]------------
	kernel BUG at arch/x86/kernel/irq_32.c:219!

We're not ISA: we have a 1:1 mapping from vectors to irqs.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

arch/x86/lguest/boot.c

@@ -586,6 +586,9 @@ static void __init lguest_init_IRQ(void)
 
 	for (i = 0; i < LGUEST_IRQS; i++) {
 		int vector = FIRST_EXTERNAL_VECTOR + i;
+		/* Some systems map "vectors" to interrupts weirdly.  Lguest has
+		 * a straightforward 1 to 1 mapping, so force that here. */
+		__get_cpu_var(vector_irq)[vector] = i;
 		if (vector != SYSCALL_VECTOR) {
 			set_intr_gate(vector, interrupt[vector]);
 			set_irq_chip_and_handler_name(i, &lguest_irq_controller,