xfs: Simplify XFS logging methods.

Rather than have a constructor to define many nearly-identical
functions, use preprocessor macros to pass down a kernel logging level
to a common function.

Signed-off-by: Jonathan Lassoff <jof@thejof.com>
Reviewed-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>