hw/smbios: Dumb down smbios_entry_add() stub

The QERR_ macros are leftovers from the days of "rich" error objects.
We've been trying to reduce their remaining use.

smbios_entry_add() is only ever called on behalf of CLI option
-smbios.  Since qemu-options.hx sets @arch_mask to QEMU_ARCH_I386 |
QEMU_ARCH_ARM, it is reachable only for these targets.  Since they
provide a real smbios_entry_add(), the stub is unreachable.

There's no point in unreachable code keeping QERR_UNSUPPORTED alive.
Dumb it down to g_assert_not_reached().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230207075115.1525-6-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>

hw/smbios/smbios-stub.c

@@ -21,11 +21,9 @@
  */
 
 #include "qemu/osdep.h"
-#include "qapi/error.h"
-#include "qapi/qmp/qerror.h"
 #include "hw/firmware/smbios.h"
 
 void smbios_entry_add(QemuOpts *opts, Error **errp)
 {
-    error_setg(errp, QERR_UNSUPPORTED);
+    g_assert_not_reached();
 }