n_hdlc: remove tracing debug prints

We can trace functions using ftrace, so there is no need for this
additional prints. Remove them.

We keep only those which print some additional info, not only function
name & "entry"/"exit".

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200219084118.26491-1-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>