target/i386: sev: Partial cleanup to sev_state global

target/i386: sev: Partial cleanup to sev_state global

The SEV code uses a pretty ugly global to access its internal state.  Now
that SEVState is embedded in SevGuestState, we can avoid accessing it via
the global in some cases.  In the remaining cases use a new global
referencing the containing SevGuestState which will simplify some future
transformations.

Signed-off-by: David Gibson <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Message-Id: <20200604064219[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>