device property: constify fwnode_get_phy_mode() argument

fwnode_get_phy_mode() does not modify the fwnode argument, merely
using it to obtain the phy-mode property value. Therefore, it can
be made const.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/E1pfdh9-00EQ8t-HB@rmk-PC.armlinux.org.ukSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/property.c

@@ -935,7 +935,7 @@ EXPORT_SYMBOL_GPL(device_get_dma_attr);
  * 'phy-connection-type', and return its index in phy_modes table, or errno in
  * error case.
  */
-int fwnode_get_phy_mode(struct fwnode_handle *fwnode)
+int fwnode_get_phy_mode(const struct fwnode_handle *fwnode)
 {
 	const char *pm;
 	int err, i;

include/linux/property.h

@@ -396,7 +396,7 @@ enum dev_dma_attr device_get_dma_attr(const struct device *dev);
 const void *device_get_match_data(const struct device *dev);
 
 int device_get_phy_mode(struct device *dev);
-int fwnode_get_phy_mode(struct fwnode_handle *fwnode);
+int fwnode_get_phy_mode(const struct fwnode_handle *fwnode);
 
 void __iomem *fwnode_iomap(struct fwnode_handle *fwnode, int index);