net: ravb: 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: 1197 at drivers/net/phy/phy_device.c:323 mdio_bus_phy_resume+0xbc/0xc8

As the Renesas Ethernet AVB 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/8ec796f47620980fdd0403e21bd8b7200b4fa1d4.1663598796.git.geert+renesas@glider.be


Signed-off-by: Jakub Kicinski <kuba@kernel.org>