net: phy: Port set/clear bits from Linux

To simply porting phy drivers from Linux to U-Boot, define
phy_set_bits() and phy_clear_bits() functions with a similar API to
those used in Linux.

The U-Boot versions of these functions include the `devad` argument
which is not present in the Linux versions, to keep them aligned with
the other phy functions in U-Boot.

Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>

include/phy.h

@@ -333,6 +333,30 @@ int gen10g_startup(struct phy_device *phydev);
 int gen10g_shutdown(struct phy_device *phydev);
 int gen10g_discover_mmds(struct phy_device *phydev);
 
+/**
+ * phy_set_bits - Convenience function for setting bits in a PHY register
+ * @phydev: the phy_device struct
+ * @devad: The MMD to read from
+ * @regnum: register number to write
+ * @val: bits to set
+ */
+static inline int phy_set_bits(struct phy_device *phydev, int devad, u32 regnum, u16 val)
+{
+	return phy_modify(phydev, devad, regnum, 0, val);
+}
+
+/**
+ * phy_clear_bits - Convenience function for clearing bits in a PHY register
+ * @phydev: the phy_device struct
+ * @devad: The MMD to write to
+ * @regnum: register number to write
+ * @val: bits to clear
+ */
+static inline int phy_clear_bits(struct phy_device *phydev, int devad, u32 regnum, u16 val)
+{
+	return phy_modify(phydev, devad, regnum, val, 0);
+}
+
 /**
  * U_BOOT_PHY_DRIVER() - Declare a new U-Boot driver
  * @__name: name of the driver