Use native bswap32 instruction when __CPU__ is x86_64 instead of generic 386 code.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@5049 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavutil/bswap.h

@@ -27,7 +27,7 @@ static always_inline uint16_t bswap_16(uint16_t x)
 
 static always_inline uint32_t bswap_32(uint32_t x)
 {
-#if __CPU__ > 386
+#if __CPU__ != 386
  __asm("bswap   %0":
       "=r" (x)     :
 #else