powerpc/powernv: Remove unused variable in pnv_pci_sriov_disable()

The local variable @iov isn't used, to remove it.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>