package/libtheora: Fix dynamic linking

libtheoraenc.so needs to be linked to libtheoradec.so in order to avoid

symbol 'th_comment_query_count': can't resolve symbol in lib '/usr/lib/libtheoraenc.so.1'

when starting Freeswitch.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>