drm/amdgpu/gfx9: fix CSIB handling

[ Upstream commit a4a4c0ae6742ec7d6bf1548d2c6828de440814a0 ]

We shouldn't return after the last section.
We need to update the rest of the CSIB.

Reviewed-by: Rodrigo Siqueira <siqueira@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>