llvmpipe: fix occlusion queries with early depth test

llvmpipe: fix occlusion queries with early depth test

for genuine early depth tests, the samplecount must be updated after depth
test but before samplemask is applied

for inferred-early or regular depth tests, the samplemask can be applied
before the depth test

Fixes: d9276ae965a ("llvmpipe: handle gl_SampleMask writing.")

fixes:
dEQP-VK.fragment_operations.early_fragment.sample_count_early_fragment_tests_depth_samples_4

Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15319>