configure: Only enable iamfdec, iamfenc when needed

Since 591e27d1e7 they would
always be compiled even when nothing uses them; for shared
builds the default linker behaviour is to include them
even when not needed.

Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

configure

@@ -3595,8 +3595,8 @@ gxf_muxer_select="pcm_rechunk_bsf"
 hds_muxer_select="flv_muxer"
 hls_demuxer_select="aac_demuxer ac3_demuxer adts_header ac3_parser eac3_demuxer mov_demuxer mpegts_demuxer"
 hls_muxer_select="mov_muxer mpegts_muxer"
-iamf_demuxer_deps="iamfdec"
-iamf_muxer_deps="iamfenc"
+iamf_demuxer_select="iamfdec"
+iamf_muxer_select="iamfenc"
 image2_alias_pix_demuxer_select="image2_demuxer"
 image2_brender_pix_demuxer_select="image2_demuxer"
 imf_demuxer_deps="libxml2"
@@ -3612,8 +3612,9 @@ matroska_muxer_select="mpeg4audio riffenc aac_adtstoasc_bsf pgs_frame_merge_bsf
 mlp_demuxer_select="mlp_parser"
 mmf_muxer_select="riffenc"
 mov_demuxer_select="iso_media riffdec"
-mov_demuxer_suggest="zlib"
+mov_demuxer_suggest="iamfdec zlib"
 mov_muxer_select="iso_media riffenc rtpenc_chain vp9_superframe_bsf aac_adtstoasc_bsf ac3_parser"
+mov_muxer_suggest="iamfenc"
 mp3_demuxer_select="mpegaudio_parser"
 mp3_muxer_select="mpegaudioheader"
 mp4_muxer_select="mov_muxer"
@@ -4084,7 +4085,7 @@ enable asm
 enable debug
 enable doc
 enable faan faandct faanidct
-enable iamf iamfdec iamfenc
+enable iamf
 enable large_tests
 enable optimizations
 enable ptx_compression