KVM: x86: Simplify msr_filter update

Replace srcu_dereference()+rcu_assign_pointer() sequence with
a single rcu_replace_pointer().

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://lore.kernel.org/r/20230107001256.2365304-4-mhal@rbox.co


Signed-off-by: Sean Christopherson <seanjc@google.com>