igb: remove unnecessary reads of PCI_CAP_ID_EXP

The PCIE capability offset is saved during PCI bus walking.  It will
remove an unnecessary search in the PCI configuration space if this
value is referenced instead of reacquiring it.
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/igb_main.c

@@ -6267,7 +6267,7 @@ s32 igb_read_pcie_cap_reg(struct e1000_hw *hw, u32 reg, u16 *value)
 	struct igb_adapter *adapter = hw->back;
 	u16 cap_offset;
 
-	cap_offset = pci_find_capability(adapter->pdev, PCI_CAP_ID_EXP);
+	cap_offset = adapter->pdev->pcie_cap;
 	if (!cap_offset)
 		return -E1000_ERR_CONFIG;
 
@@ -6281,7 +6281,7 @@ s32 igb_write_pcie_cap_reg(struct e1000_hw *hw, u32 reg, u16 *value)
 	struct igb_adapter *adapter = hw->back;
 	u16 cap_offset;
 
-	cap_offset = pci_find_capability(adapter->pdev, PCI_CAP_ID_EXP);
+	cap_offset = adapter->pdev->pcie_cap;
 	if (!cap_offset)
 		return -E1000_ERR_CONFIG;