tests/acceptance: Count multiple Tux logos displayed on framebuffer

tests/acceptance: Count multiple Tux logos displayed on framebuffer

Add a test that verifies that each core properly displays the Tux
logo on the framebuffer device.

We simply follow the OpenCV "Template Matching with Multiple Objects"
tutorial, replacing Lionel Messi by Tux:
https://docs.opencv.org/4.2.0/d4/dc6/tutorial_py_template_matching.html

When OpenCV and NumPy are installed, this test can be run using:

  $ avocado --show=app,framebuffer \
    run -t cpu:i6400 \
    tests/acceptance/machine_mips_malta.py
  JOB ID     : 54f3d8efd8674f289b8aa01a87f5d70c5814544c
  JOB LOG    : avocado/job-results/job-2020-02-01T20.52-54f3d8e/job.log
   (1/3) tests/acceptance/machine_mips_malta.py:MaltaMachineFramebuffer.test_mips_malta_i6400_framebuffer_logo_1core:
  framebuffer: found Tux at position (x, y) = (0, 0)
  PASS (3.37 s)
   (2/3) tests/acceptance/machine_mips_malta.py:MaltaMachineFramebuffer.test_mips_malta_i6400_framebuffer_logo_7cores:
  framebuffer: found Tux at position (x, y) = (0, 0)
  framebuffer: found Tux at position (x, y) = (88, 0)
  framebuffer: found Tux at position (x, y) = (176, 0)
  framebuffer: found Tux at position (x, y) = (264, 0)
  framebuffer: found Tux at position (x, y) = (352, 0)
  framebuffer: found Tux at position (x, y) = (440, 0)
  framebuffer: found Tux at position (x, y) = (528, 0)
  PASS (5.80 s)
   (3/3) tests/acceptance/machine_mips_malta.py:MaltaMachineFramebuffer.test_mips_malta_i6400_framebuffer_logo_8cores:
  framebuffer: found Tux at position (x, y) = (0, 0)
  framebuffer: found Tux at position (x, y) = (88, 0)
  framebuffer: found Tux at position (x, y) = (176, 0)
  framebuffer: found Tux at position (x, y) = (264, 0)
  framebuffer: found Tux at position (x, y) = (352, 0)
  framebuffer: found Tux at position (x, y) = (440, 0)
  framebuffer: found Tux at position (x, y) = (528, 0)
  framebuffer: found Tux at position (x, y) = (616, 0)
  PASS (6.67 s)
  RESULTS    : PASS 3 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
  JOB TIME   : 16.79 s

If the AVOCADO_CV2_SCREENDUMP_PNG_PATH environment variable is set, the
test will save the screenshot with matched squares to it.

Test inspired by the following post:
https://www.mips.com/blog/how-to-run-smp-linux-in-qemu-on-a-mips64-release-6-cpu/
Kernel built with the following Docker file:
https://github.com/philmd/qemu-testing-blob/blob/malta_i6400/mips/malta/mips64el/Dockerfile

Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20200201204751.17810-1-f4bug@amsat.org>