cdvdgigaherz: Dual layer DVD type/layer 1 start LSN fixes

For dual layer DVDs, CDVDgetDualInfo() should return the first layer 1
LSN, not the last layer 0 LSN, which is what GetLayerBreakAddress()
returns. This matches what the internal ISO reader returns.

Also, PTP DVDs should return a value of 1 for the media type, not 2.

Finally, adjust the CDVDgetDualInfo() return value so PCSX2 correctly
recognises dual layer DVDs.

plugins/cdvdGigaherz/src/CDVD.cpp

@@ -290,18 +290,18 @@ s32  CALLBACK CDVDgetDualInfo(s32* dualType, u32* _layer1start)
 	{
 	case 1:
 		*dualType = 1;
-		*_layer1start = src->GetLayerBreakAddress();
-		return 1;
+		*_layer1start = src->GetLayerBreakAddress() + 1;
+		return 0;
 	case 2:
 		*dualType = 2;
-		*_layer1start = src->GetLayerBreakAddress();
-		return 1;
+		*_layer1start = src->GetLayerBreakAddress() + 1;
+		return 0;
 	case 0:
 		*dualType = 0;
 		*_layer1start = 0;
-		return 1;
+		return 0;
 	}
-	return 0;
+	return -1;
 }
 
 int lastReadInNewDiskCB=0;

plugins/cdvdGigaherz/src/Windows/IOCtlSrc.cpp

@@ -579,7 +579,7 @@ s32 IOCtlSrc::GetMediaType()
 			{
 				//PTP
 				mediaTypeCached = true;
-				mediaType = 2;
+				mediaType = 1;
 				return mediaType;
 			}