Remove rbegin() from array.hpp

This was added during debugging when attempting to add in partial_sum()
to replicate device behavior when using calculate_strides(). In this case
this isn't needed

src/targets/gpu/kernels/include/migraphx/kernels/array.hpp

@@ -149,9 +149,6 @@ struct array
     constexpr T* begin() { return d; }
     constexpr const T* begin() const { return d; }
 
-    constexpr T* rbegin() { return d[N -1]; }
-    constexpr const T* rbegin() const { return d[N - 1]; }
-
     constexpr T* end() { return d + size(); }
     constexpr const T* end() const { return d + size(); }