KVM: Documentation: Fix up cpuid page

0x4b564d00 and 0x4b564d01 belong to KVM_FEATURE_CLOCKSOURCE2.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20200416155913.267562-1-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>