drm/amdgpu: Enable DISABLE_BARRIER_WAITCNT for Arcturus

In previous gfx9 parts, S_BARRIER shader instructions are implicitly
S_WAITCNT 0 instructions as well. This setting turns off that
mechanism in Arcturus and beyond. With this, shaders must follow the
ISA guide insofar as putting in explicit S_WAITCNT operations even
after an S_BARRIER.

v2: Fix patch title to list component

Signed-off-by: Joseph Greathouse <Joseph.Greathouse@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>