drm/amd/display: Remove duplicate entry from log_mask
As pointed out by kbuild test robot and Julia Lawall.
CC: Julia Lawall <julia.lawall@lip6.fr>
CC: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>