[d3d9] Fix software cursor texture format

The new code expects texture reads to be in linear space, so we need
to use an sRGB format here.

src/d3d9/d3d9_swapchain.cpp

@@ -732,7 +732,7 @@ namespace dxvk {
 
       m_blitter->setCursorTexture(
         cursorSize,
-        VK_FORMAT_B8G8R8A8_UNORM,
+        VK_FORMAT_B8G8R8A8_SRGB,
         (void *) pCursorBitmap);
   }