xtensa: ISS: don't panic in rs_init

[ Upstream commit 23411c72

 ]

While alloc_tty_driver failure in rs_init would mean we have much bigger
problem, there is no reason to panic when tty_register_driver fails
there. It can fail for various reasons.

So handle the failure gracefully. Actually handle them both while at it.
This will make at least the console functional as it was enabled earlier
by console_initcall in iss_console_init. Instead of shooting down the
whole system.

We move tty_port_init() after alloc_tty_driver(), so that we don't need
to destroy the port in case the latter function fails.

Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-xtensa@linux-xtensa.org
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723074317.32690-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>