FROMGIT: sched: Don't report SCHED_FLAG_SUGOV in sched_getattr()

SCHED_FLAG_SUGOV is supposed to be a kernel-only flag that userspace
cannot interact with. However, sched_getattr() currently reports it
in sched_flags if called on a sugov worker even though it is not
actually defined in a UAPI header. To avoid this, make sure to
clean-up the sched_flags field in sched_getattr() before returning to
userspace.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210727101103.2729607-3-qperret@google.com

Bug: 190237315
(cherry picked from commit 7ad721bf
 git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git

 sched/core)
Signed-off-by: Quentin Perret <qperret@google.com>
Change-Id: Ib998d497fc38a7f8e6ccb80119336c9ac30719b7