hw/xen: add stubs for various functions

hw/xen: add stubs for various functions

Those symbols are used by system/physmem.c, and are called only if
xen_enabled() (which happens only if CONFIG_XEN is set and xen is
available).

So we can crash the stubs in case those are called, as they are linked
only when CONFIG_XEN is not set.

Acked-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250317183417.285700-13-pierrick.bouvier@linaro.org>