lockd: Remove lockd/debug.h

lockd: Remove lockd/debug.h

The lockd include structure has unnecessary indirection. The header
include/linux/lockd/debug.h is consumed only by fs/lockd/lockd.h,
creating an extra compilation dependency and making the code harder
to navigate.

Fold the debug.h definitions directly into lockd.h and remove the
now-redundant header. This reduces the include tree depth and makes
the debug-related definitions easier to find when working on lockd
internals.

Build-tested with lockd built as module and built-in.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>