phy: core: Simplify API of_phy_simple_xlate() implementation

Simplify of_phy_simple_xlate() implementation by API
class_find_device_by_of_node().

Also correct comments to mark its parameter @dev as unused instead of
@args in passing.

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
Cc: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20241213-phy_core_fix-v6-6-40ae28f5015a@quicinc.com


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