drm/amdgpu: read TRUNCATE_COORD_MODE on gfx12

drm/amdgpu: read TRUNCATE_COORD_MODE on gfx12

TA_CNTL2.TRUNCATE_COORD_MODE selects whether texture coordinate
truncation is D3D9/GL/Vulkan conformant. gfx11 reads it and reports it to
userspace via AMDGPU_IDS_FLAGS_CONFORMANT_TRUNC_COORD, but gfx12 never
read it, so the flag was always reported as 0 and userspace fell back to
the non-conformant path.

Read it in gfx_v12_0_constants_init() like gfx11 does.

Fixes: 52cb80c12e8a ("drm/amdgpu: Add gfx v12_0 ip block support (v6)")
Signed-off-by: Qiang Yu <Qiang.Yu@amd.com>
Reviewed-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 4261cbc7b03f1f56e95aeaf1492b8690fa5a253e)
Cc: stable@vger.kernel.org