r600g: avoid using pb* helper we are loosing previous cpu cycle with it

r600g: avoid using pb* helper we are loosing previous cpu cycle with it

r600g is up to a point where all small CPU cycle matter and pb* turn
high on profile. It's mostly because pb try to be generic and thus
trigger unecessary check for r600g driver. To avoid having too much
abstraction & too much depth in the call embedded everythings into
r600_bo. Make code simpler & faster. The performance win highly depend
on the CPU & application considered being more important on slower CPU
and marginal/unoticeable on faster one.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>