drm/amdgpu/sdma5.2: limit wptr workaround to sdma 5.2.1

The workaround seems to cause stability issues on other
SDMA 5.2.x IPs.

Fixes: a03ebf11 ("drm/amdgpu/sdma5.2: Update wptr registers as well as doorbell")
Closes: drm/amd#3556


Acked-by: Ruijing Dong <ruijing.dong@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>