ITS: test tonemap only if COLOR_BARS exists

Also change test_test_patterns to not require COLOR_BARS.

Readability cleanup in test_tonemap:
Defined constants
  YUV_H = 480
  YUV_W = 640
  # fixed patch coordinates
  WNORM = 1.0 / N_BARS - 2 * DELTA
  YNORM = 0.0
  HNORM = 1.0

Created a helper function to compute the xnorm value for the color patch

bug: 153112079
Change-Id: I4fa90cb79073cf855f604635484a5f217ea3508b
2 files changed