hwrng: cavium - fix NULL but dereferenced coccicheck error

Fix following coccicheck warning:
./drivers/char/hw_random/cavium-rng-vf.c:182:17-20: ERROR:
pdev is NULL but dereferenced.
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Reviewed-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/cavium-rng-vf.c

@@ -179,7 +179,7 @@ static int cavium_map_pf_regs(struct cavium_rng *rng)
 	pdev = pci_get_device(PCI_VENDOR_ID_CAVIUM,
 			      PCI_DEVID_CAVIUM_RNG_PF, NULL);
 	if (!pdev) {
-		dev_err(&pdev->dev, "Cannot find RNG PF device\n");
+		pr_err("Cannot find RNG PF device\n");
 		return -EIO;
 	}