drm/amdgpu: move UVD IB test into common code v2

Since we now raise the clocks from begin_use() we don't need
a separate function for each hw generation any more.

v2: remove unintentional lowering of the UVD clocks, fix typos for CIK hw.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>