net: sh_eth: Fix PHY state warning splat during system resume

Since commit 744d23c7 ("net: phy: Warn about incorrect
mdio_bus_phy_resume() state"), a warning splat is printed during system
resume with Wake-on-LAN disabled:

	WARNING: CPU: 0 PID: 626 at drivers/net/phy/phy_device.c:323 mdio_bus_phy_resume+0xbc/0xe4

As the Renesas SuperH Ethernet driver already calls phy_{stop,start}()
in its suspend/resume callbacks, it is sufficient to just mark the MAC
responsible for managing the power state of the PHY.

Fixes: fba863b8 ("net: phy: make PHY PM ops a no-op if MAC driver manages PHY PM")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/c6e1331b9bef61225fa4c09db3ba3e2e7214ba2d.1663598886.git.geert+renesas@glider.beSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/renesas/sh_eth.c

@@ -2029,6 +2029,8 @@ static int sh_eth_phy_init(struct net_device *ndev)
 	if (mdp->cd->register_type != SH_ETH_REG_GIGABIT)
 		phy_set_max_speed(phydev, SPEED_100);
 
+	/* Indicate that the MAC is responsible for managing PHY PM */
+	phydev->mac_managed_pm = true;
 	phy_attached_info(phydev);
 
 	return 0;