xfs: kill support/debug.[ch]

The remaining functionality in debug.[ch] is effectively just assert
handling, conditional debug definitions and hex dumping. The hex
dumping and assert function can be moved into the new printk module,
while the rest can be moved into top-level header files. This allows
fs/xfs/support/debug.[ch] to be completely removed from the
codebase.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>