kernel/futex: Make futex_wait_requeue_pi() only call fixup_owner()

A small cleanup that allows for fixup_pi_state_owner() only to be called
from fixup_owner(), and make requeue_pi uniformly call fixup_owner()
regardless of the state in which the fixup is actually needed. Of course
this makes the caller's first pi_state->owner != current check redundant,
but that should't really matter.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210226175029.50335-2-dave@stgolabs.net