drivers: eth_smsc911x_priv: Remove obsolete macros
drivers: eth_smsc911x_priv: Remove obsolete macros

Back with commit a1b77fd589 huge chunk of code was automatically
refactored using a script, which in turn left some macros meaningless

Signed-off-by: Hristo Mitrev <acb0e75baff311fdd4d915f4ccdeb5c34ddae8ea@gmail.com>

zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr