AGNi kernel v3.8.1 haydn (stable)

• BUGFIX release for v3.8

ufs: Implement UFS 3.1 Host Performance Booster from OnePlus 9
ufs: allow HPB/TW/HID features for haydn UFS-3.1 vendors MICRON/SAMSUNG
dts: add 90Hz display option for Haydn [AOSP only, user request, slight color shift]
block: Implement & enable by default SSG IOsched (SamSung Generic IO scheduler)
memory management & rcu: Implement lot of upstream commits
Switch to KernelSU v0.6.1 (stable) branch
disable debugging serial drivers and cleancache