x86: Documentation/i386/IO-APIC.txt: fix description

The description of the interrupt routing doesn't match the (nice) diagram.
Signed-off-by: NNick Andrew <nick@nick-andrew.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Documentation/i386/IO-APIC.txt

@@ -70,7 +70,7 @@ Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD:
 
 These INTA-D PCI IRQs are always 'local to the card', their real meaning
 depends on which slot they are in. If you look at the daisy chaining diagram,
-a card in slot4, issuing INTA IRQ, it will end up as a signal on PIRQ2 of
+a card in slot4, issuing INTA IRQ, it will end up as a signal on PIRQ4 of
 the PCI chipset. Most cards issue INTA, this creates optimal distribution
 between the PIRQ lines. (distributing IRQ sources properly is not a
 necessity, PCI IRQs can be shared at will, but it's a good for performance