drm/amdgpu: Set CP_HQD_PQ_CONTROL.RPTR_BLOCK_SIZE correctly

Remove the accidental shifts on the values of RPTR_BLOCK_SIZE
in gfx_v8-v11. The bug essentially always programs the
corresponding fields to zero instead of the correct value.
The hardware clamps the min value to 5 so this resulted in a
value of 5 being programmed.

Signed-off-by: Haohui Mai <ricetons@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>