xfs: remove __KERNEL__ from debug code

There is no reason the remaining kernel-only debug code needs to
remain kernel-only. Kill the __KERNEL__ part of the defines, and let
userspace handle the debug code appropriately.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>