net: ti: am65-cpsw-nuss: invoke phy_config() in driver's .start callback

net: ti: am65-cpsw-nuss: invoke phy_config() in driver's .start callback

Currently, the phy_config() API is invoked by the driver only once since it
has been probed. While this works in general, it doesn't allow the driver
to bring the PHY back to its default reset state. As a result, the driver
might not be able to recover the PHY from a bad state. To address this,
move phy_config() into the driver's start callback (am65_cpsw_start()).

Apart from providing the means to recover the PHY in the event of failure,
the implementation is in line with the idea of "reset and configure" that
is already followed by am65_cpsw_start() when it comes to programming the
CPSW MAC.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>