powerpc/pseries: fix potential memory leak in init_cpu_associativity()

If the vcpu_associativity alloc memory successfully but the
pcpu_associativity fails to alloc memory, the vcpu_associativity
memory leaks.

Fixes: d62c8dee

 ("powerpc/pseries: Provide vcpu dispatch statistics")
Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Reviewed-by: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/1671003983-10794-1-git-send-email-wangyufen@huawei.com