drm/amd/display: only collect data if debug gamut_remap is available

Color gamut_remap state log may be not available for some hw versions,
so prevent null pointer dereference by checking if there is a function
to collect data for this hw version.

Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>