lavc/hevcdsp: Fix compilation for arm with --disable-neon.

(cherry picked from commit 1d523ea8)

libavcodec/hevcdsp.c

@@ -259,6 +259,6 @@ int i = 0;
 
     if (ARCH_X86)
         ff_hevc_dsp_init_x86(hevcdsp, bit_depth);
-    if (ARCH_ARM)
+    if (HAVE_NEON)
         ff_hevcdsp_init_arm(hevcdsp, bit_depth);
 }