target/arm: Convert FCVT* (vector, integer) to decodetree

target/arm: Convert FCVT* (vector, integer) to decodetree

Remove handle_2misc_64 as these were the last insns decoded
by that function.  Remove helper_advsimd_f16to[su]inth as unused;
we now always go through helper_vfp_to[su]hh or a specialized
vector function instead.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241211163036.2297116-65-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>