e4m3fn: 8bit floating point format with 4bit exponent, 3bit mantissa
and no infinities (finite only)
e5m2: 8bit floating point format with 5bit exponent, 2bit mantissa
and with infinities.
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35434>