rd890: clear IO-APIC before setup

Add function "clear_ioapic" before "setup_ioapic" for RD890 northbridge
like it is done for SB700 and SB800 chipsets ("amd/cimx/sb{7,8}00").

No functionality change is noticed.

Change-Id: I1fd87692d8bf35c166141c9b7a6a1e748c19a636
Signed-off-by: Aladyshev Konstantin <aladyshev@nicevt.ru>
Reviewed-on: http://review.coreboot.org/2045
Tested-by: build bot (Jenkins)
Reviewed-by: Zheng Bao <zheng.bao@amd.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/northbridge/amd/cimx/rd890/late.c

@@ -123,6 +123,7 @@ static void ioapic_init(struct device *dev)
 
 	pci_write_config32(dev, 0xF8, 0x1);
 	ioapic_base = pci_read_config32(dev, 0xFC) & 0xfffffff0;
+	clear_ioapic(ioapic_base);
 	setup_ioapic(ioapic_base, 1);
 }