KVM: x86: Add X86EMUL_F_MSR and X86EMUL_F_DT_LOAD to aid canonical checks

KVM: x86: Add X86EMUL_F_MSR and X86EMUL_F_DT_LOAD to aid canonical checks

Add emulation flags for MSR accesses and Descriptor Tables loads, and pass
the new flags as appropriate to emul_is_noncanonical_address().  The flags
will be used to perform the correct canonical check, as the type of access
affects whether or not CR4.LA57 is consulted when determining the canonical
bit.

No functional change is intended.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20240906221824.491834-3-mlevitsk@redhat.com
[sean: split to separate patch, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>