softfloat: Pad array size in pick_nan_muladd

softfloat: Pad array size in pick_nan_muladd

While all indices into val[] should be in [0-2], the mask
applied is two bits.  To help static analysis see there is
no possibility of read beyond the end of the array, pad the
array to 4 entries, with the final being (implicitly) NULL.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20241203203949.483774-6-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>