hvsi: don't panic on tty_register_driver failure

hvsi: don't panic on tty_register_driver failure

The alloc_tty_driver failure is handled gracefully in hvsi_init. But
tty_register_driver is not. panic is called if that one fails.

So handle the failure of tty_register_driver gracefully too. This will
keep at least the console functional as it was enabled earlier by
console_initcall in hvsi_console_init. Instead of shooting down the
whole system.

This means, we disable interrupts and restore hvsi_wait back to
poll_for_state().

Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723074317.32690-3-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>