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/dcn20/dcn20_mpc.c:455:70-75: WARNING:
conversion to bool not needed here
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>