hw/isa/i82378: Propagate error if PC_SPEAKER device creation failed

In commit 40f8214 ("hw/audio/pcspk: Inline pcspk_init()")
we neglected to give a change to the caller to handle failed
device creation cleanly. Respect the caller API contract and
propagate the error if creating the PC_SPEAKER device ever
failed. This avoid yet another bad API use to be taken as
example and copy / pasted all over the code base.

Reported-by: Bernhard Beschow <shentey@gmail.com>
Suggested-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Bernhard Beschow <shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20231020171509.87839-5-philmd@linaro.org>

hw/isa/i82378.c

@@ -105,7 +105,9 @@ static void i82378_realize(PCIDevice *pci, Error **errp)
     /* speaker */
     pcspk = isa_new(TYPE_PC_SPEAKER);
     object_property_set_link(OBJECT(pcspk), "pit", OBJECT(pit), &error_fatal);
-    isa_realize_and_unref(pcspk, isabus, &error_fatal);
+    if (!isa_realize_and_unref(pcspk, isabus, errp)) {
+        return;
+    }
 
     /* 2 82C37 (dma) */
     isa_create_simple(isabus, "i82374");