lockdep: Make __bfs(.match) return bool

The "match" parameter of __bfs() is used for checking whether we hit a
match in the search, therefore it should return a boolean value rather
than an integer for better readability.

This patch then changes the return type of the function parameter and the
match functions to bool.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-9-boqun.feng@gmail.com