lavc/libkvazaar: fix incompatible pointer type.

lavc/libkvazaar: fix incompatible pointer type.

fix the waring: libavcodec/libkvazaar.c:210:27: warning: passing argument 3 of ‘av_image_copy’ from incompatible pointer type [-Wincompatible-pointer-types]
                           frame->data, frame->linesize,
                           ^~~~~
In file included from libavcodec/libkvazaar.c:31:0:
./libavutil/imgutils.h:119:6: note: expected ‘const uint8_t ** {aka const unsigned char **}’ but argument is of type ‘uint8_t * const* {aka unsigned char * const*}’
 void av_image_copy(uint8_t *dst_data[4], int dst_linesizes[4],

Signed-off-by: Jun Zhao <mypopydev@gmail.com>