avcodec/fft: fix INTERL macro on 3dnow

The commit b7c16a3f2c ("x86: fft: Port to
cpuflags") breaks the opus decoder in ffmpeg when compiling for 3dnow. The
output is audible, but there's a lot of noise.

The reason for the breakage is that the commit unintentionally changed the
INTERL macro so that it is empty when compiling for 3dnow. This patch
fixes it.

Signed-off-by: Mikulas Patocka <mikulas@twibright.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/x86/fft.asm

@@ -199,7 +199,7 @@ SECTION .text
     vextractf128  %4 %+ H(%5), %3, 0
     vextractf128   %4(%5 + 1), %2, 1
     vextractf128  %4 %+ H(%5 + 1), %3, 1
-%elif cpuflag(sse)
+%elif cpuflag(sse) || cpuflag(3dnow)
     mova     %3, %2
     unpcklps %2, %1
     unpckhps %3, %1