target/i386: sev: Rename QSevGuestInfo

target/i386: sev: Rename QSevGuestInfo

At the moment this is a purely passive object which is just a container for
information used elsewhere, hence the name.  I'm going to change that
though, so as a preliminary rename it to SevGuestState.

That name risks confusion with both SEVState and SevState, but I'll be
working on that in following patches.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200604064219.436242-4-david@gibson.dropbear.id.au>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>