gstaacparse: add parse adif program_config_element() for fetch correct channel number

Submitted by Lyon

Link to original bug (#785476)

Description

Created attachment 356456
3 channel adif clip

when I'm trying to get correct channel number of one adif file.
I found that in gstaacparse, for adif format, it just assume channels = 2, without parse the program_config_element() to get the correct channel num

Please see attached 3 channel adif file for test

Attachment 356456, "3 channel adif clip":
AAC_LC_32kHz_120kbps_3_ADIF.aac

Version: 1.12.2