[][kernel][common][audio][Add mt7986-si3218x machine driver to Kconfig and Makefile]

[Description]
Add mt7986-si3218x machine driver to Kconfig and Makefile
for backport mt7986 audio driver from kernel 6.7.

[Release-log]
N/A

Change-Id: I1b1e93471fd502a2db3b93a0fbf331ff910fd041
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8265959
1 file changed