iris: Use converted depth in clear_depth_stencil

Until recently, the depth value from glClearBufferfv wasn't clamped.

Before then, this patch enabled the driver to fail the clearbuffer-depth
piglit test with INTEL_DEBUG=nofc. This is because convert_depth_value
relies on the assumption that the depth value is clamped.

Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7410>
1 file changed