samples: tflite-micro: Use FVP for test validation

What is changed?
 - Replaced printk with printf in the sample

Why do we need this change?
 - Running the sample with fvp just prints the below output and not
   the complete logs that we expect:
    `sender 0: Sending inference`
   We get the expected output with CONFIG_LOG_IMMEDIATE=y but,
   its not ideal. printf works without the config and plus it
   looks a better fit in the current sample than printk.

This change is validate using `mps3/corstone300/fvp`.

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