x86/xstate: don't clobber or leak state when using XSAVES

x86/xstate: don't clobber or leak state when using XSAVES

Commit 4d27280572 ("x86/xsaves: fix overwriting between non-lazy/lazy
xsaves") switched to always saving full state when using compacted
format (which is the only one XSAVES allows). It didn't, however, also
adjust the restore side: In order to save full state, we also need to
make sure we always load full state, or else the subject vCPU's state
would get clobbered by that of the vCPU which happened to last have in
use the respective component(s).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>