drm/i915: Add support of SDVO on Ibexpeak PCH

SDVO on Ibexpeak PCH with Ironlake is multiplexed with
HDMIB port, and only has SDVOB port.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 8de8194..b4ff815 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2629,6 +2629,9 @@
 #define  HSYNC_ACTIVE_HIGH      (1 << 3)
 #define  PORT_DETECTED          (1 << 2)
 
+/* PCH SDVOB multiplex with HDMIB */
+#define PCH_SDVOB	HDMIB
+
 #define HDMIC   0xe1150
 #define HDMID   0xe1160