avutil: add AVX-512 flags

libavutil/tests/cpu.c

@@ -73,6 +73,7 @@ static const struct {
     { AV_CPU_FLAG_BMI1,      "bmi1"       },
     { AV_CPU_FLAG_BMI2,      "bmi2"       },
     { AV_CPU_FLAG_AESNI,     "aesni"      },
+    { AV_CPU_FLAG_AVX512,    "avx512"     },
 #endif
     { 0 }
 };