lustre: delete linux/lustre_debug.h

There was only one macro in here, LL_CDEBUG_PAGE().  So open code it in
the 2 places it was used so that the developer seeing it can see just
how horrid it really is, and they can remove it as I doubt it really is
ever needed anymore.  But for now, keep the same functionality and
remove a whole file (with a duplicate name of other files in the lustre
repo, another confusion...)

Cc: Peng Tao <bergwolf@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>