backports: rcupdate: Add rcu_replace_pointer

rcu_replace_pointer() was added in upstream commit a63fc6b75cca ("rcu:
Upgrade rcu_swap_protected() to rcu_replace_pointer()") and is now used
by the mt76 driver.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
1 file changed