bcache: Convert to lock_cmp_fn

Replace one of bcache's lockdep_set_novalidate_class() usage with the
newly introduced custom lock nesting annotation.

[peterz: changelog]
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Coly Li <colyli@suse.de>
Link: https://lkml.kernel.org/r/20230509195847.1745548-2-kent.overstreet@linux.dev