staging: lustre: use CONFIG_PROC_FS

Don't rely on a "custom" LPROCFS define, it's not needed, just check for
the real thing.  This will let us delete a whole .h file that is not
being used for anything other than one #define.

Cc: Andreas Dilger <andreas.dilger@intel.com>
Cc: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>