net: renesas: rswitch: Add .[gs]et_link_ksettings support

Add .[gs]et_link_ksettings support by using
phy_ethtool_[gs]et_link_ksettings() functions.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230807003231.1552062-3-yoshihiro.shimoda.uh@renesas.com


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