KVM: selftests: Remove duplicate VM creation in memslot_perf_test

KVM: selftests: Remove duplicate VM creation in memslot_perf_test

Remove a spurious call to __vm_create_with_one_vcpu() that was introduced
by a merge gone sideways.

Fixes: eb5618911af0 ("Merge tag 'kvmarm-6.2' of https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD")
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/r/20230118092133.320003-2-gshan@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>