Canonicalize Composite{SVD}

[mzgubic]

Making an issue out of #388

julia> using ChainRules

julia> using LinearAlgebra

julia> x = rand(3, 2);

julia> F = svd(x);

julia> y, pb = rrule(getproperty, F, :V);

julia> c = pb(rand(3, 2))[2]
Composite{SVD{Float64,Float64,Array{Float64,2}}}(V = [0.17383499380772904 0.39005912263976916; 0.45401136256238694 0.857760693263997; 0.5536276381177541 0.3029145326674041],)

julia> canonicalize(c)
ERROR: ArgumentError: Composite fields do not match primal fields.
Composite fields: (:V,). Primal (SVD{Float64,Float64,Array{Float64,2}}) fields: (:U, :S, :Vt)

Will do what Seth said #388 (comment)