powerpc/powernv/sriov: Remove unused but set variable 'phb'

Gcc report warning as follows:

arch/powerpc/platforms/powernv/pci-sriov.c:602:25: warning:
 variable 'phb' set but not used [-Wunused-but-set-variable]
  602 |  struct pnv_phb        *phb;
      |                         ^~~

This variable is not used, so this commit removing it.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200727171112.2781-1-weiyongjun1@huawei.com

arch/powerpc/platforms/powernv/pci-sriov.c

@@ -599,10 +599,8 @@ static int pnv_pci_vf_resource_shift(struct pci_dev *dev, int offset)
 static void pnv_pci_sriov_disable(struct pci_dev *pdev)
 {
 	u16                    num_vfs, base_pe;
-	struct pnv_phb        *phb;
 	struct pnv_iov_data   *iov;
 
-	phb = pci_bus_to_pnvhb(pdev->bus);
 	iov = pnv_iov_get(pdev);
 	num_vfs = iov->num_vfs;
 	base_pe = iov->vf_pe_arr[0].pe_number;