KVM: x86/mmu: Move initial kvm_mmu_set_mask_ptes() call into MMU proper

mainline inclusion
from mainline-v5.13-rc1
commit ec761cfd
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=ec761cfd353f3b37072cda095d245c155c7cdb0f



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Move kvm_mmu_set_mask_ptes() into mmu.c as prep for future cleanup of the
mask initialization code.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-16-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>