drm/amd/display: fix if == else warning

Fix the following coccicheck warning:

drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c:98:8-10:
WARNING: possible condition with no effect (if == else)

Reviewed-by: Zhan Liu <zhan.liu@amd.com>
Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>