float_dsp: Replace arch optimization ifdefs by if cascade

Arch-specific optimizations are handled this way everywhere else.

libavutil/float_dsp.c

@@ -124,15 +124,14 @@ av_cold void avpriv_float_dsp_init(AVFloatDSPContext *fdsp, int bit_exact)
     fdsp->butterflies_float = butterflies_float_c;
     fdsp->scalarproduct_float = avpriv_scalarproduct_float_c;
 
-#if   ARCH_AARCH64
-    ff_float_dsp_init_aarch64(fdsp);
-#elif ARCH_ARM
-    ff_float_dsp_init_arm(fdsp);
-#elif ARCH_PPC
-    ff_float_dsp_init_ppc(fdsp, bit_exact);
-#elif ARCH_X86
-    ff_float_dsp_init_x86(fdsp);
-#endif
+    if (ARCH_AARCH64)
+        ff_float_dsp_init_aarch64(fdsp);
+    if (ARCH_ARM)
+        ff_float_dsp_init_arm(fdsp);
+    if (ARCH_PPC)
+        ff_float_dsp_init_ppc(fdsp, bit_exact);
+    if (ARCH_X86)
+        ff_float_dsp_init_x86(fdsp);
 }
 
 #ifdef TEST