[gTests] Create new gTests for bn_fwd_train and bn_bwd

[xinlipn]

Create gTests to cover cases without saved Mean and saved InvVar, equivalent to e.g. the command below

./bin/MIOpenDriver bnormbfp16 -n 1 -c 2 -H 24 -W 16 -m 1 --forw 1 -b 0 -s 0 -r 0 -t 1 --layout NCHW

[bghimireamd]

I do not see bn bwd cpu handle both "saved mean" and "no saved mean"

[xinlipn]

I do not see bn bwd cpu handle both "saved mean" and "no saved mean"

Hi @bghimireamd , that's a good catch. I have this change locally, but but bn_bwd doesn't seem to pass yet with it. I have just committed the change to ComputeCPUBNBwd

[amd-hsivasun]

Imported to ROCm/rocm-libraries