We're supposed to map a floating-point value too large to be represented
as fp16 to infinity, however round-to-zero naturally rounds it down to
the largest representable fp16 number instead. The blob emits a bunch of
fixup code to work around this, but instead we can just do what all the
other drivers seem to do and use round-to-nearest-even instead.
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10897>
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