i2c_probe: Fix argument checking logic

The default value of bus is None, so the test should explicitly check
bus is not None. Otherwise, bus=0 will result in assert error.

BUG=chrome-os-partner:26909
TEST=run i2c_probe test with bus=0, there should be assert error.

Change-Id: I008a34868d4ae4ce3ed185145d0cb5cf673c9a81
Reviewed-on: https://chromium-review.googlesource.com/190277
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Queue: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
1 file changed