Remove x86_emulate_ops::guest_has_long_mode along with its implementation,
emulator_guest_has_long_mode(). It has been unused since commit
1d0da94c ("KVM: x86: do not go through ctxt->ops when emulating rsm").

No functional change intended.
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://lore.kernel.org/r/20230718101809.1249769-1-mhal@rbox.coSigned-off-by: Sean Christopherson <seanjc@google.com>