KVM: selftests: Delete dead ucall code

Delete a bunch of code related to ucall handling from
smaller_maxphyaddr_emulation_test. The only thing
smaller_maxphyaddr_emulation_test needs to check is that the vCPU exits
with UCALL_DONE after the second vcpu_run().

Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221102184654.282799-4-dmatlack@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>