[][kernel][common][audio][Add mt7986-si3218x machine driver]

[Description]
Add mt7986-si3218x machine driver to fit backport mt7986 audio driver
from kernel 6.7.

[Release-log]
N/A

Change-Id: I9cf7577a2e6dd7ebc2febd165f1eb6c6398e15c9
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8265958
1 file changed