n_hdlc: convert debuglevel use to pr_debug
With pr_debug we have a fine-grained control about debugging prints. So
convert the use of global debuglevel variable and tests to a commonly
used pr_debug. And drop debuglevel completely.
This also implicitly adds a loglevel to the messages (KERN_DEBUG) as it
was missing on most of them.
And also use __func__ instead of function names explicitly typed.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200219084118.26491-3-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>