drm/amdgpu/uvd: reduce IB parsing overhead on UVD5+ (v2)

UVD 5 and newer do not have the same placement limitations
as older chips, so skip the first pass since it's just
overhead on chips where we don't have to force placement.

v2: fix inverted logic

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