[PATCH net] net: enetc: add missing static descriptor and inline keyword

Fix the build warnings when CONFIG_FSL_ENETC_MDIO is not enabled.
The detailed warnings are shown as follows.

include/linux/fsl/enetc_mdio.h:62:18: warning: no previous prototype for function 'enetc_hw_alloc' [-Wmissing-prototypes]
      62 | struct enetc_hw *enetc_hw_alloc(struct device *dev, void __iomem *port_regs)
         |                  ^
include/linux/fsl/enetc_mdio.h:62:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
      62 | struct enetc_hw *enetc_hw_alloc(struct device *dev, void __iomem *port_regs)
         | ^
         | static
8 warnings generated.

Fixes: 6517798dd343 ("enetc: Make MDIO accessors more generic and export to include/linux/fsl")
Cc: stable@vger.kernel.org
Reported-by: kernel test robot <redacted>
Closes: https://lore.kernel.org/oe-kbuild-all/202410102136.jQHZOcS4-lkp@intel.com/ (local)
Signed-off-by: Wei Fang <wei.fang@nxp.com>
---
 include/linux/fsl/enetc_mdio.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/fsl/enetc_mdio.h b/include/linux/fsl/enetc_mdio.h
index df25fffdc0ae..623ccfcbf39c 100644
--- a/include/linux/fsl/enetc_mdio.h
+++ b/include/linux/fsl/enetc_mdio.h

@@ -59,7 +59,8 @@ static inline int enetc_mdio_read_c45(struct mii_bus *bus, int phy_id,
 static inline int enetc_mdio_write_c45(struct mii_bus *bus, int phy_id,
 				       int devad, int regnum, u16 value)
 { return -EINVAL; }
-struct enetc_hw *enetc_hw_alloc(struct device *dev, void __iomem *port_regs)
+static inline struct enetc_hw *enetc_hw_alloc(struct device *dev,
+					      void __iomem *port_regs)
 { return ERR_PTR(-EINVAL); }
 
 #endif

-- 
2.34.1