lavu/crc: Fix doxy group definition

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/crc.h

@@ -25,6 +25,12 @@
 #include <stddef.h>
 #include "attributes.h"
 
+/**
+ * @defgroup lavu_crc32 CRC32
+ * @ingroup lavu_crypto
+ * @{
+ */
+
 typedef uint32_t AVCRC;
 
 typedef enum {
@@ -71,4 +77,8 @@ const AVCRC *av_crc_get_table(AVCRCId crc_id);
 uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
                 const uint8_t *buffer, size_t length) av_pure;
 
+/**
+ * @}
+ */
+
 #endif /* AVUTIL_CRC_H */