net: caif: inline register_ldisc

net: caif: inline register_ldisc

register_ldisc only calls tty_register_ldisc. Inline register_ldisc into
the only caller of register_ldisc, i.e. caif_ser_init. Now,
caif_ser_init is symmetric to caif_ser_exit in this regard.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210302062214.29627-14-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>