Un-obfuscate DQ_PINLOCK, remove DQ_PINLOCK->mutex_lock->spin_lock macros,
call spin_lock directly, remove extraneous cookie holdover from old xfs
code, and change lock type to spinlock_t.

SGI-PV: 970382
SGI-Modid: xfs-linux-melb:xfs-kern:29742a
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Donald Douwsma <donaldd@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>