of: unittest: drop assertions for GPIO hog messages

These have now been demoted to debug and are normally hidden. Drop the
assertions entirely.

Suggested-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Rob Herring <robh@kernel.org>