KVM: x86: compile out TDP MMU on 32-bit systems

mainline inclusion
from mainline-v5.12-rc1
commit 897218ff
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=897218ff7cf19290ec2d69652ce673d8ed6fedeb



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The TDP MMU assumes that it can do atomic accesses to 64-bit PTEs.
Rather than just disabling it, compile it out completely so that it
is possible to use for example 64-bit xchg.

To limit the number of stubs, wrap all accesses to tdp_mmu_enabled
or tdp_mmu_page with a function.  Calls to all other functions in
tdp_mmu.c are eliminated and do not even reach the linker.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

conflict:
	arch/x86/include/asm/kvm_host.h
	arch/x86/kvm/mmu/mmu.c

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>