Adds support for ATI SB400 bridge.

Reference: /n/sources/patch/applied/pci-ati
Date: Tue Mar 27 22:34:01 CES 2007
Signed-off-by: lorenzobivens@gmail.com

--- /sys/src/9/pc/pci.c	Tue Mar 27 22:33:40 2007
+++ /sys/src/9/pc/pci.c	Tue Mar 27 22:33:30 2007
@@ -659,6 +659,7 @@
 	{ 0x10DE, 0x00D1, nil, nil },		// NVIDIA nForce 3
 	{ 0x1166, 0x0200, nil, nil },		// ServerWorks ServerSet III LE
 	{ 0x1002, 0x4377, nil, nil },		// ATI Radeon Xpress 200M
+	{ 0x1002, 0x4372, nil, nil },		// ATI SB400
 };
 
 typedef struct Slot Slot;