Add VSX wiener filter implementation

Added implementation of the wiener filter.

Performance improvement on Power9:

wiener_chroma_8bpc_c: 42696.7
wiener_chroma_8bpc_vsx: 25196.7
wiener_luma_8bpc_c: 43143.1
wiener_luma_8bpc_vsx: 25188.3

Performance improvement on Power8:

wiener_chroma_8bpc_c: 44507.5
wiener_chroma_8bpc_vsx: 22216.3
wiener_luma_8bpc_c: 44335.6
wiener_luma_8bpc_vsx: 22220.3