drm/amd/display: remove conversion to bool in dc_link_ddc.c

drm/amd/display: remove conversion to bool in dc_link_ddc.c

The '>' expression itself is bool, no need to convert it to bool again.
This fixes the following coccicheck warning:

drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c:602:28-33: WARNING:
conversion to bool not needed here

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>