FROMGIT: rust: sync: condvar: Add wait_interruptible_freezable()

To support waiting for a `CondVar` as a freezable process, add a
wait_interruptible_freezable() function.

Binder needs this function in the appropriate places to freeze a process
where some of its threads are blocked on the Binder driver.

[Boqun: Capitalize the title and reword the commit log]

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20250204-condvar-freeze-v2-1-804483096260@google.com

Bug: 388786466
(cherry picked from commit 39dfd06783c0e256f420695ea85d95a5f471bc22
 git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git

 lockdep-for-tip)
Change-Id: I04c41d20868898a3371ebafa54e4afb76edc762e
Signed-off-by: Alice Ryhl <aliceryhl@google.com>