ANDROID: GKI: ENABLE CONFIG_SCHED_CLASS_EXT in android16-kernel6.12

As discussed in 397116737, we need to enable the CONFIG_SCHED_CLASS_EXT
configuration on Android 16 with kernel 6.12.

Bug: 397116737
Bug: 408943580
Change-Id: I6c33ead044a65547c7594883b56a8571603edd8d
Signed-off-by: xieliujie <xieliujie@oppo.com>
[jstultz: Minor tweaks to commit message]
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>