wimax: fix build issue when debugfs is disabled

As reported by Toralf Förster and Randy Dunlap.

- http://linuxwimax.org/pipermail/wimax/2009-January/000460.html

- http://lkml.org/lkml/2009/1/29/279

The definitions needed for the wimax stack and i2400m driver debug
infrastructure was, by mistake, compiled depending on CONFIG_DEBUG_FS
(by them being placed in the debugfs.c files); thus the build broke in
2.6.29-rc3 when debugging was enabled (CONFIG_WIMAX_DEBUG) and
DEBUG_FS was disabled.

These definitions are always needed if debug is enabled at compile
time (independently of DEBUG_FS being or not enabled), so moving them
to a file that is always compiled fixes the issue.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>