IVGCVSW-1957: Improve warning message in Network::Optimize()
IVGCVSW-1957: Improve warning message in Network::Optimize()

* Added data type to layer not supported warnign message for more clarity

Change-Id: I7a933ad32e6a0288e8dd712a7a1dea016e4bd9a2

ARM-software/armnn,ARM-software/armnn,ARM-software/armnn