target/arm: Fix decode of FMOV (hp) vs MOVI

target/arm: Fix decode of FMOV (hp) vs MOVI

The decode of FMOV (vector, immediate, half-precision) vs
invalid cases of MOVI are incorrect.

Fixes RISU mismatch for invalid insn 0x2f01fd31.

Fixes: 70b4e6a4457 ("arm/translate-a64: add FP16 FMOV to simd_mod_imm")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20240524232121.284515-6-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>