Adjust kernel configs for new low-memory killer

Android 11 and beyond on kernel 4.9 or newer can use a new low memory
killer, lmkd. On kernel side it requires support for pidfd and psi. Both
are backported to the android-4.9-q common kernel as well, which we have
merged in.

Disable the old memory killer and enable PSI to allow using the new LMK.

Issue: FP3-A11#63
Issue: FP3-A13#31
Change-Id: Ia257a011e7ad8d11933900714cdc5f5e19048db0