lavu/x86/tx_float: fix FMA3 implying AVX2 is available

It's the other way around - AVX2 implies FMA3 is available.

libavutil/x86/tx_float.asm

@@ -100,7 +100,7 @@ SECTION .text
 ; %6 - temporary register (for avx only)
 ; %7 - temporary register (for avx only, enables vgatherdpd (AVX2) if FMA3 is set)
 %macro LOAD64_LUT 5-7
-%if %0 > 6 && cpuflag(fma3)
+%if %0 > 6 && cpuflag(avx2)
     pcmpeqd %6, %6 ; pcmpeqq has a 0.5 throughput on Zen 3, this has 0.25
     movapd xmm%7, [%3 + %4] ; float mov since vgatherdpd is a float instruction
     vgatherdpd %1, [%2 + xmm%7*8], %6 ; must use separate registers for args
@@ -1208,5 +1208,5 @@ FFT_SPLIT_RADIX_DEF 131072
 
 %if ARCH_X86_64
 FFT_SPLIT_RADIX_FN avx
-FFT_SPLIT_RADIX_FN fma3
+FFT_SPLIT_RADIX_FN avx2
 %endif

libavutil/x86/tx_float_init.c

@@ -32,7 +32,7 @@ void ff_fft32_float_avx     (AVTXContext *s, void *out, void *in, ptrdiff_t stri
 void ff_fft32_float_fma3    (AVTXContext *s, void *out, void *in, ptrdiff_t stride);
 
 void ff_split_radix_fft_float_avx (AVTXContext *s, void *out, void *in, ptrdiff_t stride);
-void ff_split_radix_fft_float_fma3(AVTXContext *s, void *out, void *in, ptrdiff_t stride);
+void ff_split_radix_fft_float_avx2(AVTXContext *s, void *out, void *in, ptrdiff_t stride);
 
 av_cold void ff_tx_init_float_x86(AVTXContext *s, av_tx_fn *tx)
 {
@@ -87,10 +87,15 @@ av_cold void ff_tx_init_float_x86(AVTXContext *s, av_tx_fn *tx)
 #if ARCH_X86_64
             else if (s->m == 32)
                 TXFN(ff_fft32_float_fma3, 1, 8, 2);
-            else if (s->m >= 64 && s->m <= 131072 && !(s->flags & AV_TX_INPLACE))
-                TXFN(ff_split_radix_fft_float_fma3, 1, 8, 2);
 #endif
         }
+
+#if ARCH_X86_64
+        if (EXTERNAL_AVX2_FAST(cpu_flags)) {
+            if (s->m >= 64 && s->m <= 131072 && !(s->flags & AV_TX_INPLACE))
+                TXFN(ff_split_radix_fft_float_avx2, 1, 8, 2);
+        }
+#endif
     }
 
     if (gen_revtab)