net: eth-phy: Demote missing phy-handle log message to debug

Reduce the missing phy-handle log message to debug message. It is
possible for ethernet DT node to have no phy-handle e.g. in case
of a fixed-link connection. Furthermore, drop the FEC: prefix,
which is a copy-paste error and rather print the ethernet device
name.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>