hfs: Convert tree_lock to mutex

tree_lock is used as mutex so make it a mutex.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
LKML-Reference: <20100907125056.416332114@linutronix.de>

diff --cc fs/hfs/bfind.c
Simple merge

diff --cc fs/hfs/btree.c
Simple merge

diff --cc fs/hfs/btree.h
Simple merge