lib/test_vmalloc.c: Rename kvfree_rcu() to kvfree_rcu_mightsleep()

lib/test_vmalloc.c: Rename kvfree_rcu() to kvfree_rcu_mightsleep()

The kvfree_rcu() macro's single-argument form is deprecated.  Therefore
switch to the new kvfree_rcu_mightsleep() variant. The goal is to
avoid accidental use of the single-argument forms, which can introduce
functionality bugs in atomic contexts and latency bugs in non-atomic
contexts.

Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>