Add the function read_and_check_msr_entry() which just pulls some code
out of nested_vmx_store_msr().  This will be useful as reusable code in
upcoming patches.
Reviewed-by: NLiran Alon <liran.alon@oracle.com>
Reviewed-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NAaron Lewis <aaronlewis@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>