rtmpcrypt: Do the xtea decryption in little endian mode

The XTEA algorithm operates on 32 bit numbers, not on byte sequences.
The XTEA implementation in libavutil is written assuming big endian
numbers, while the rtmpe signature encryption assumes little endian.

This fixes rtmpe communication with rtmpe servers that use signature
type 8 (XTEA), e.g. crunchyroll.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtmpcrypt.c

@@ -186,7 +186,7 @@ static void rtmpe8_sig(const uint8_t *in, uint8_t *out, int key_id)
     struct AVXTEA ctx;
 
     av_xtea_init(&ctx, rtmpe8_keys[key_id]);
-    av_xtea_crypt(&ctx, out, in, 1, NULL, 0);
+    av_xtea_le_crypt(&ctx, out, in, 1, NULL, 0);
 }
 
 static void rtmpe9_sig(const uint8_t *in, uint8_t *out, int key_id)