KVM: x86/mmu: Use leaf-only loop for walking TDP SPTEs when changing SPTE

mainline inclusion
from mainline-v5.13-rc1
commit aaaac889
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I7S3VQ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aaaac889cf63a6c2e5f4b20c20cccf5aeb78bd51



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Use the leaf-only TDP iterator when changing the SPTE in reaction to a
MMU notifier.  Practically speaking, this is a nop since the guts of the
loop explicitly looks for 4k SPTEs, which are always leaf SPTEs.  Switch
the iterator to match age_gfn_range() and test_age_gfn() so that a future
patch can consolidate the core iterating logic.

No real functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>