KVM: x86: Introduce get_untagged_addr() in kvm_x86_ops and call it in emulator

Introduce a new interface get_untagged_addr() to kvm_x86_ops to untag
the metadata from linear address.  Call the interface in linearization
of instruction emulator for 64-bit mode.

When enabled feature like Intel Linear Address Masking (LAM) or AMD Upper
Address Ignore (UAI), linear addresses may be tagged with metadata that
needs to be dropped prior to canonicality checks, i.e. the metadata is
ignored.

Introduce get_untagged_addr() to kvm_x86_ops to hide the vendor specific
code, as sadly LAM and UAI have different semantics.  Pass the emulator
flags to allow vendor specific implementation to precisely identify the
access type (LAM doesn't untag certain accesses).

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
Link: https://lore.kernel.org/r/20230913124227.12574-9-binbin.wu@linux.intel.com


[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>