Update readme for nn_test
-CMSIS DSP_Lib example arm_nnexample_cifar10 for
- Cortex-M4 and Cortex-M7.
+CMSIS DSP_Lib example arm_nnexample_nn_test for
+ Cortex-M3, Cortex-M4 and Cortex-M7.
The example is configured for uVision Simulator.
