MLBEDSW-8927 Extend PAD/MIRROR_PAD support to 3D tensors
Created utility functions for getting the padding values for different axes which are not dependent on the input tensor being 4-dimensional.
Change-Id: If3398f7e665f5dae39b184efecbb8caed439f225 Signed-off-by: Jacob Bohlin jacob.bohlin@arm.com