powerpc: Fix for Pegasos keyboard and mouse

[See http://lists.ozlabs.org/pipermail/linuxppc-dev/2010-October/086424.html
and followups. Part of the commit message is directly copied from that.]

Commit 540c6c39 tries to find i8042 IRQs in
the device-tree but doesn't fall back to the old hardcoded 1 and 12 in all
failure cases.

Specifically, the case where the device-tree contains nothing matching
pnpPNP,303 or pnpPNP,f03 doesn't seem to be handled well. It sort of falls
through to the old code, but leaves the IRQs set to 0.
Signed-off-by: Gabriel Paubert <paubert@iram.es>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/setup-common.c

@@ -602,6 +602,10 @@ int check_legacy_ioport(unsigned long base_port)
 		 * name instead */
 		if (!np)
 			np = of_find_node_by_name(NULL, "8042");
+		if (np) {
+			of_i8042_kbd_irq = 1;
+			of_i8042_aux_irq = 12;
+		}
 		break;
 	case FDC_BASE: /* FDC1 */
 		np = of_find_node_by_type(NULL, "fdc");