[PATCH -next] PCI: imx6: Fix build error unused-function

[Ren Zhijie]

If CONFIG_PM_SLEEP is not set,
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-, will be failed, like this:

drivers/pci/controller/dwc/pci-imx6.c:973:13: error: ‘imx6_pcie_host_exit’ defined but not used [-Werror=unused-function]
 static void imx6_pcie_host_exit(struct dw_pcie_rp *pp)
             ^~~~~~~~~~~~~~~~~~~
drivers/pci/controller/dwc/pci-imx6.c:904:13: error: ‘imx6_pcie_stop_link’ defined but not used [-Werror=unused-function]
 static void imx6_pcie_stop_link(struct dw_pcie *pci)
             ^~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[4]: *** [drivers/pci/controller/dwc/pci-imx6.o] Error 1

These two functions imx6_pcie_host_exit() and imx6_pcie_stop_link() only be called by imx6_pcie_suspend_noirq(), which was warpped by CONFIG_PM_SLEEP.
To fix build error unused-function, use __maybe_unused to attach them.

Fixes: 25ae5434c3de ("PCI: imx6: Reformat suspend callback to keep symmetric with resume")
Signed-off-by: Ren Zhijie <renzhijie2@xxxxxxxxxx>
---
 drivers/pci/controller/dwc/pci-imx6.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 55e109d1ab27..533f5ef68e94 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -901,7 +901,7 @@ static int imx6_pcie_start_link(struct dw_pcie *pci)
 	return 0;
 }
 
-static void imx6_pcie_stop_link(struct dw_pcie *pci)
+static void __maybe_unused imx6_pcie_stop_link(struct dw_pcie *pci)
 {
 	struct device *dev = pci->dev;
 
@@ -970,7 +970,7 @@ static int imx6_pcie_host_init(struct dw_pcie_rp *pp)
 	return ret;
 }
 
-static void imx6_pcie_host_exit(struct dw_pcie_rp *pp)
+static void __maybe_unused imx6_pcie_host_exit(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct imx6_pcie *imx6_pcie = to_imx6_pcie(pci);
-- 
2.17.1