hps_accel/conv2d_20: Clarify source
hps_accel/conv2d_20: Clarify source

Specify source model for data in this file.

Signed-off-by: Alan Green <97e77871b5fcc4941bebceb4338c97c1fd149f8c@google.com>

google/CFU-Playground,google/CFU-Playground,google/CFU-Playground,google/CFU-Playground