UPSTREAM: net: stmmac: honor error code from stmmac_dt_phy()

Honor error code from stmmac_dt_phy() instead of always
returning -ENODEV.

No functional change intended.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit ce339abc
https://github.com/torvalds/linux.git

)
Signed-off-by: Vinod Koul <vkoul@kernel.org>