net: hifemac_mdio: use log_msg_ret() correctly, report error by dev_err()

The initial commit used log_msg_ret() wrongly. Fix that by moving error
report to a separate dev_err() call and shrink the first argument of
log_msg_ret() to no more than 4 chars.

Fixes: 6b5c8d98 ("net: add hifemac_mdio MDIO bus driver for HiSilicon platform")

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>