KVM: x86/mmu: fix an incorrect comment in kvm_mmu_new_pgd()

There is no function named kvm_mmu_ensure_valid_pgd().

Fix the comment and remove the pair of braces to conform to Linux kernel
coding style.

Signed-off-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221128214709.224710-1-wei.liu@kernel.org


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