dot falls back to `LinearAlgebra/src/generic.jl`

Hi,

I have another difficulty. It seems `dot` falls back to `LinearAlgebra/src/generic.jl` in both 0.7 and 0.6.4

Can it be fixed by?

`import Base.LinAlg: dot, norm
dot(a::ArrayFire.AFArray,b::ArrayFire.AFArray) = ArrayFire.dot(a,b,UInt32(0),UInt32(0))[1]`

Also I had to extract the first element, it would be better for ArrayFire.dot to return a scalar.

Thank you

Best regards