mft: map MFVideoFormat_ARGB32 to VLC_CODEC_BGRA

The documentation [1] says that it's equivalent to D3DFMT_A8R8G8B8. And the d3d10 porting documentation [2] says it's equivalent to DXGI_FORMAT_B8G8R8A8_UNORM.

[1] https://learn.microsoft.com/en-us/windows/win32/medfound/video-subtype-guids [2] https://learn.microsoft.com/en-us/windows/win32/direct3d10/d3d10-graphics-programming-guide-resources-legacy-formats