KVM: x86/mmu: Add '__func__' in rmap_printk()

Given the common pattern:

rmap_printk("%s:"..., __func__,...)

we could improve this by adding '__func__' in rmap_printk().

Signed-off-by: Stephen Zhang <stephenzhangzsd@gmail.com>
Message-Id: <1611713325-3591-1-git-send-email-stephenzhangzsd@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>