net: introduce helpers to get PHY interface mode from a device/ofnode

Add helpers ofnode_read_phy_mode() and dev_read_phy_mode() to parse the
"phy-mode" / "phy-connection-type" property. Add corresponding UT test.

Use them treewide.

This allows us to inline the phy_get_interface_by_name() into
ofnode_read_phy_mode(), since the former is not used anymore.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Tested-by: Patrice Chotard <patrice.chotard@foss.st.com>

include/dm/ofnode.h

@@ -12,6 +12,7 @@
 #include <dm/of.h>
 #include <dm/of_access.h>
 #include <log.h>
+#include <phy_interface.h>
 
 /* Enable checks to protect against invalid calls */
 #undef OF_CHECKS
@@ -1231,4 +1232,16 @@ const char *ofnode_conf_read_str(const char *prop_name);
  */
 ofnode ofnode_get_phy_node(ofnode eth_node);
 
+/**
+ * ofnode_read_phy_mode() - Read PHY connection type from a MAC node
+ *
+ * This function parses the "phy-mode" / "phy-connection-type" property and
+ * returns the corresponding PHY interface type.
+ *
+ * @mac_node:	ofnode containing the property
+ * Return: one of PHY_INTERFACE_MODE_* constants, PHY_INTERFACE_MODE_NONE on
+ *	   error
+ */
+phy_interface_t ofnode_read_phy_mode(ofnode mac_node);
+
 #endif