scsi: qedf: Use pci_get_dsn()

Replace the open-coded implementation for reading the PCIe DSN with
pci_get_dsn().

The original code used a for-loop that looped over each of the 8 bytes
and copied them into a temporary buffer. pci_get_dsn() uses two calls to
pci_read_config_dword, and correctly bitwise ORs them into a u64. Thus,
we can simplify the snprintf significantly using %016llX on a u64 value.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/scsi/qedf/qedf_main.c

@@ -1577,8 +1577,7 @@ static void qedf_setup_fdmi(struct qedf_ctx *qedf)
 {
 	struct fc_lport *lport = qedf->lport;
 	struct fc_host_attrs *fc_host = shost_to_fc_host(lport->host);
-	u8 buf[8];
-	int i, pos;
+	u64 dsn;
 
 	/*
 	 * fdmi_enabled needs to be set for libfc to execute FDMI registration.
@@ -1591,18 +1590,11 @@ static void qedf_setup_fdmi(struct qedf_ctx *qedf)
 	 */
 
 	/* Get the PCI-e Device Serial Number Capability */
-	pos = pci_find_ext_capability(qedf->pdev, PCI_EXT_CAP_ID_DSN);
-	if (pos) {
-		pos += 4;
-		for (i = 0; i < 8; i++)
-			pci_read_config_byte(qedf->pdev, pos + i, &buf[i]);
-
+	dsn = pci_get_dsn(qedf->pdev);
+	if (dsn)
 		snprintf(fc_host->serial_number,
-		    sizeof(fc_host->serial_number),
-		    "%02X%02X%02X%02X%02X%02X%02X%02X",
-		    buf[7], buf[6], buf[5], buf[4],
-		    buf[3], buf[2], buf[1], buf[0]);
-	} else
+		    sizeof(fc_host->serial_number), "%016llX", dsn);
+	else
 		snprintf(fc_host->serial_number,
 		    sizeof(fc_host->serial_number), "Unknown");