kprobes: Tell lockdep about kprobe nesting

Since the kprobe handlers have protection that prohibits other handlers from
executing in other contexts (like if an NMI comes in while processing a
kprobe, and executes the same kprobe, it will get fail with a "busy"
return). Lockdep is unaware of this protection. Use lockdep's nesting api to
differentiate between locks taken in INT3 context and other context to
suppress the false warnings.

Link: https://lore.kernel.org/r/20201102160234.fa0ae70915ad9e2b21c08b85@kernel.org

Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>