KVM: VMX: Drop intermediate "guest" field from msr_autostore

KVM: VMX: Drop intermediate "guest" field from msr_autostore

Drop the intermediate "guest" field from vcpu_vmx.msr_autostore as the
value saved on VM-Exit isn't guaranteed to be the guest's value, it's
purely whatever is in hardware at the time of VM-Exit.  E.g. KVM's only
use of the store list at the momemnt is to snapshot TSC at VM-Exit, and
the value saved is always the raw TSC even if TSC-offseting and/or
TSC-scaling is enabled for the guest.

And unlike msr_autoload, there is no need differentiate between "on-entry"
and "on-exit".

No functional change intended.

Cc: Jim Mattson <jmattson@google.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Manali Shukla <manali.shukla@amd.com>
Link: https://patch.msgid.link/20251206001720.468579-36-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>