Revert "sched/fair: set_load_weight() must also call reweight_task() for SCHED_IDLE tasks"

This reverts commit b37f1c53 which is
commit d3296052 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: I01e5e8bef8b6612aca025fe76d055d727514a8ea
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>