ANDROID: Zap kernel/sched/android.h stubs

Long ago with android-mainline, kernel/sched/android.h was added
to include stub functions for out-of-tree logic that we wanted
to remove from android-mainline without breaking vendor drivers
that relied on these stubs.

Unfortunately, when the android release branches (android14-6.1
and android15-6.6) forked from android-mainline, the stubs were
kept.

In some cases, the functionality dropped was re-added to the
release branches, but using new function names. Drivers that
continued to use the old names, would then end up using the stub
impelementations, likely without noticing.

Lets try to clean this up by removing the stub header.

This should not affect the GKI KABI, and pre-existing modules
should continue to work, but when modules are re-build, they
may run into build issues and will need tweaks to remove the
old stub functions.

Bug: 332588830
Change-Id: I516913f2e4c36e6edbffb3c12b633a158ba04287
Signed-off-by: John Stultz <jstultz@google.com>