lib/vsprintf: Remove static_branch_likely() from __ptr_to_hashval().

Using static_branch_likely() to signal that ptr_key has been filled is a
bit much given that it is not a fast path.

Replace static_branch_likely() with bool for condition and a memory
barrier for ptr_key.

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lkml.kernel.org/r/20220729154716.429964-2-bigeasy@linutronix.de