x86 avx: fix cvtt bounds #39

Job	Run time
x86-xop	47m 19s
sleef	54m 8s
gcc-qemu (-O3, 16, riscv64, riscv64, riscv64, ubuntu-24.04)	46m 16s
gcc-qemu (16, loongarch64, loongarch64, loong64, ubuntu-24.04)	49m 10s
gcc-16 (ubuntu-24.04-arm, true)	29m 27s
x86 (-march=x86-64-v4)	54m 18s
gcc-qemu (16, s390x, s390x, s390x, ubuntu-24.04)	51m 5s
gcc-16 (ubuntu-24.04, -ffast-math)	42m 58s
gcc-16 (ubuntu-24.04-arm, arm-linux-gnueabihf, -mcpu=cortex-a32 -mfpu=crypto-neon-fp-armv8, true)	39m 4s
gcc-16 (ubuntu-24.04-arm, arm-linux-gnueabihf, true)	40m 16s
gcc-16 (ubuntu-24.04)	48m 44s
x86 (-march=x86-64-v2)	44m 21s
x86 (-march=x86-64 -maes -mpclmul)	44m 31s
x86 (-DSIMDE_NATURAL_VECTOR_SIZE=256 -march=x86-64-v3 -mavx512bw -mavx512vl)	49m 4s
gcc-qemu (16, riscv64, riscv64, riscv64, ubuntu-24.04)	1h 9m 6s
gcc-16 (ubuntu-24.04-arm)	28m 40s
x86 (-march=x86-64-v4 -mcx16 -mxsave -mpclmul -mfsgsbase -mrdrnd -mhle -mrdseed -maes -mclflushop...	55m 57s
gcc-16 (ubuntu-24.04-arm, arm-linux-gnueabihf, -march=armv7-a+simd+neon-fp16, true)	38m 43s
x86 (-march=x86-64-v3)	43m 34s
x86 (-march=x86-64-v4 -mcx16 -mxsave -mpclmul -mfsgsbase -mrdrnd -mhle -mrdseed -maes -mclflushop...	52m 58s
	15h 29m 39s

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