brlocks/lglocks: clean up code

brlocks/lglocks: clean up code

lglocks and brlocks are currently generated with some complicated macros
in lglock.h.  But there's no reason I can see to not just use common
utility functions that get pointers to the lglock.

Since there are at least two users it makes sense to share this code in a
library.

This will also make it later possible to dynamically allocate lglocks.

In general the users now look more like normal function calls with
pointers, not magic macros.

The patch is rather large because I move over all users in one go to keep
it bisectable.  This impacts the VFS somewhat in terms of lines changed.
But no actual behaviour change.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>