reiserfs: cleanup path functions

This patch cleans up some redundancies in the reiserfs tree path code.

decrement_bcount() is essentially the same function as brelse(), so we use
that instead.

decrement_counters_in_path() is exactly the same function as pathrelse(), so
we kill that and use pathrelse() instead.

There's also a bit of cleanup that makes the code a bit more readable.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>