samples: tflite-micro: Use FVP for test validation

What is changed?
 - Updated the board qualifier for MPS3 to `mps3/corstone300/fvp`

Why do we need this change?
 - To validate the sample with FVP by default since QEMU doesn't
   model the NPU.

Signed-off-by: Sudan Landge <sudan.landge@arm.com>