configure, libavcodec/Makefile: Fix avrn dependencies

The avrn decoder actually only needs one thing: The MJPEG decoder.
Instead the Makefile made it compile mjpegdec and configure required
some of the prerequisites of the MJPEG decoder (exif and jpegtables).
Even if all the prerequisites of the MJPEG decoder were required, it
would still not make the MJPEG decoder usable, because for that
the MJPEG decoder needs to be in the list of codecs in codec_list.c.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

configure

@@ -2688,7 +2688,7 @@ atrac3p_decoder_select="mdct sinewin"
 atrac3pal_decoder_select="mdct sinewin"
 atrac9_decoder_select="mdct"
 av1_decoder_select="cbs_av1"
-avrn_decoder_select="exif jpegtables"
+avrn_decoder_select="mjpeg_decoder"
 bink_decoder_select="blockdsp hpeldsp"
 binkaudio_dct_decoder_select="mdct rdft dct sinewin wma_freqs"
 binkaudio_rdft_decoder_select="mdct rdft sinewin wma_freqs"

libavcodec/Makefile

@@ -231,7 +231,7 @@ OBJS-$(CONFIG_AURA_DECODER)            += cyuv.o
 OBJS-$(CONFIG_AURA2_DECODER)           += aura.o
 OBJS-$(CONFIG_AV1_DECODER)             += av1dec.o
 OBJS-$(CONFIG_AV1_CUVID_DECODER)       += cuviddec.o
-OBJS-$(CONFIG_AVRN_DECODER)            += avrndec.o mjpegdec.o
+OBJS-$(CONFIG_AVRN_DECODER)            += avrndec.o
 OBJS-$(CONFIG_AVRP_DECODER)            += r210dec.o
 OBJS-$(CONFIG_AVRP_ENCODER)            += r210enc.o
 OBJS-$(CONFIG_AVS_DECODER)             += avs.o