[][Refactor MT7986 thermal temperature formula]

[Description]
Refactor MT7986 thermal temperature calculation formula to
prevent loss of floating-point accuracy.

[Release-log]
N/A

Change-Id: I65d76d2f4d389d2ee127429a0835acd91726fcce
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4769470
1 file changed