modetest: Create a GAMMA_LUT property blob all the time, not just for DRM_FORMAT_C8
The set_gamma() function initializes the gamma_lut array but only creates a blob object if (fourcc == DRM_FORMAT_C8). This makes it ignore the computed gamma LUT and instead set the GAMMA_LUT property to the blob ID 0, disabling the GAMMA_LUT hardware completely.
Fix this by always creating the property blob.
Signed-off-by: Aaron Plattner aplattner@nvidia.com