target/i386: sev: Move local structure definitions into .c file

target/i386: sev: Move local structure definitions into .c file

Neither QSevGuestInfo nor SEVState (not to be confused with SevState) is
used anywhere outside target/i386/sev.c, so they might as well live in
there rather than in a (somewhat) exposed header.

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: <20200604064219.436242-3-david@gibson.dropbear.id.au>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>