net: sun8i-emac: Downgrade printf during probe to debug

This just prints the PHY mode taken from the devicetree. It does not
need to be printed during every boot, and also avoids an unwanted
line break for the "net: " reporting line.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>