While being conditionally used for TARGET_I386 in hmp-commands-info.hx,
hmp_info_sev() is declared for all targets. Reduce its declaration
to target including "monitor/hmp-target.h". This is a minor cleanup.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211007161716.453984-23-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>