Enable NEON on aarch64

The original reason NEON was disabled was lack of runtime detection.  It
should be runtime detected on Linux.

NEON is also required for ARMv8, so it's reasonable to expect every
aarch64 host to have it.  FFTW should still work without NEON, but I
don't know of any aarch64 CPU without it to test this on.

Signed-off-by: Trent Piepho <tpiepho@gmail.com>

fftw.spec

@@ -296,13 +296,12 @@ for ((i=0; i<2; i++)) ; do
 done
 %endif
 
-# No NEON run time detection, not all ARM SoCs have NEON
-#%ifarch %{arm}
-## Compile support for NEON instructions
-#for ((i=0; i<2; i++)) ; do
-#    prec_flags[i]+=" --enable-neon"
-#done
-#%endif
+%ifarch %{arm64}
+# Compile support for NEON instructions
+for ((i=0; i<2; i++)) ; do
+    prec_flags[i]+=" --enable-neon"
+done
+%endif
 
 #%ifarch ppc ppc64
 ## Compile support for Altivec instructions
@@ -527,6 +526,7 @@ done
 %changelog
 * Mon Mar 27 2023 Trent Piepho <tpiepho@gmail.com> - 3.3.10-6
 - Enable AVX2 on x86-86
+- Enable NEON on aarch64
 
 * Thu Mar 02 2023 Orion Poplawski <orion@nwra.com> - 3.3.10-5
 - Use make macros