tools/liblockdep: Fix debug_check thinko in mutex destroy

In mutex destroy code currently we pass to debug_check_no_locks_freed()

    [mem_from, mem_end)

address region. But debug_check_no_locks_freed() accepts

    mem_from, mem_*len*

i.e. second parameter is region length, not end address. And it was
always so, starting from 2006 (fbb9ce95

 "lockdep: core").

Fix it, or else on a mutex destroy we wrongly check
much-wider-than-mutex region and can find not-yet-released other locks
there and wrongly report BUGs on them.

Signed-off-by: Kirill Smelkov <kirr@nexedi.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>