hvc/xen: fix error path in xen_hvc_init() to always register frontend driver

The xen_hvc_init() function should always register the frontend driver,
even when there's no primary console — as there may be secondary consoles.
(Qemu can always add secondary consoles, but only the toolstack can add
the primary because it's special.)

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20231020161529.355083-3-dwmw2@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: dwmw2

drivers/tty/hvc/hvc_xen.c

@@ -588,7 +588,7 @@ static int __init xen_hvc_init(void)
 		ops = &dom0_hvc_ops;
 		r = xen_initial_domain_console_init();
 		if (r < 0)
-			return r;
+			goto register_fe;
 		info = vtermno_to_xencons(HVC_COOKIE);
 	} else {
 		ops = &domU_hvc_ops;
@@ -597,7 +597,7 @@ static int __init xen_hvc_init(void)
 		else
 			r = xen_pv_console_init();
 		if (r < 0)
-			return r;
+			goto register_fe;
 
 		info = vtermno_to_xencons(HVC_COOKIE);
 		info->irq = bind_evtchn_to_irq_lateeoi(info->evtchn);
@@ -622,6 +622,7 @@ static int __init xen_hvc_init(void)
 	}
 
 	r = 0;
+ register_fe:
 #ifdef CONFIG_HVC_XEN_FRONTEND
 	r = xenbus_register_frontend(&xencons_driver);
 #endif