Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index dcd7857..d35e300 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -136,7 +136,7 @@
  * @hndlr: Link state callback for the network device
  * @iface: PHY data interface type
  *
- * Returns a pointer to the phy_device if successfull.  NULL otherwise
+ * Returns a pointer to the phy_device if successful.  NULL otherwise
  */
 struct phy_device *of_phy_connect(struct net_device *dev,
 				  struct device_node *phy_np,