Fixes coccicheck warning:

drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c:1003:4-9: WARNING: Comparison to bool
drivers/gpu/drm/amd/amdgpu/sdma_v4_0.c:1083:5-11: WARNING: Comparison to bool
Acked-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NZheng Bin <zhengbin13@huawei.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>