drm/amdgpu: config HDP_MISC_CNTL.READ_BUFFER_WATERMARK

To fix applications running across multiple GPU config hang.

Signed-off-by: Xiaogang Chen <xiaogang.chen@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>