target/i386/sev: Declare system-specific functions in 'sev.h'

"sysemu/sev.h" is only used from x86-specific files. Let's move it
to include/hw/i386, and merge it with target/i386/sev.h.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211007161716.453984-16-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
6 files changed