drm/amdgpu: Use legacy TLB flush for gfx943

Invalidate TLBs via a legacy flush request (flush_type=0) prior to the
heavyweight flush requests (flush_type=2) in gmc_v9_0.c. This is
temporarily required to mitigate a bug causing CPC UTCL1 to return stale
translations after invalidation requests in address range mode.

v2: squash in long term fix "drm/amdgpu: disable extra gfx943 legacy flush on rev1+"

Signed-off-by: Graham Sider <Graham.Sider@amd.com>
Reviewed-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>