Revert "sched/deadline: Fix warning in migrate_enable for boosted tasks"

This reverts commit b600d304 which is
commit 0664e2c3 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I32c30f4a6f04a32216a83f4959002f19eacd91dc
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>