[PATCH -next] e1000e: Fix 'defined but not used' warning

[Bixuan Cui]

Fix the warning while disable CONFIG_PM_SLEEP:

drivers/net/ethernet/intel/e1000e/netdev.c:6926:12: warning:
    ‘e1000e_pm_prepare’ defined but not used [-Wunused-function]
static int e1000e_pm_prepare(struct device *dev)
            ^~~~~~~~~~~~~~~~~

Signed-off-by: Bixuan Cui <cuibix...@huawei.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c 
b/drivers/net/ethernet/intel/e1000e/netdev.c
index f1c9debd9f3b..d2e4653536c5 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -6923,7 +6923,7 @@ static int __e1000_resume(struct pci_dev *pdev)
        return 0;
 }
 
-static int e1000e_pm_prepare(struct device *dev)
+static __maybe_unused int e1000e_pm_prepare(struct device *dev)
 {
        return pm_runtime_suspended(dev) &&
                pm_suspend_via_firmware();
-- 
2.17.1