KVM: VMX: Move the comment of CR4.MCE handling right above the code

Move the comment about keeping the hosts CR4.MCE loaded in hardware above
the code that actually modifies the hardware CR4 value.

No functional change indented.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20230410125017.1305238-3-xiaoyao.li@intel.com


[sean: elaborate in changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>