UPSTREAM: sched/uclamp: Fix a deadlock when enabling uclamp static key

The following splat was caught when setting uclamp value of a task:

  BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:49

   cpus_read_lock+0x68/0x130
   static_key_enable+0x1c/0x38
   __sched_setscheduler+0x900/0xad8

Fix by ensuring we enable the key outside of the critical section in
__sched_setscheduler()

Bug: 254441685
Fixes: 46609ce22703 ("sched/uclamp: Protect uclamp fast path code with static key")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200716110347.19553-4-qais.yousef@arm.com


(cherry picked from commit e65855a52b479f98674998cb23b21ef5a8144b04)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I9b33882f72b2f5a8bb8a1e077e7785f3462d1cee