r600g: always clear query memory

r600g: always clear query memory

According to the hw documentation, the driver needs to:
- allocate 128 bits for each possible DB
- clear the 128 bits for each possible DB
- write 1 to bits 127 and 63 for upper DBs that don't
exist on a particular asic

Previously we were only doing these steps if the
asic had less than the max possible DBs.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>