isdn: capi, drop useless pr_debugs

capi have many pr_debugs in tty_operations hooks to print only a
functions name. We have better debugging aids in the kernel many years
now. So remove these useless pr_debugs.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20210505091928.22010-34-jslaby@suse.cz


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