net: marvell: prestera: Add length macros for prestera_ip_addr

net: marvell: prestera: Add length macros for prestera_ip_addr

Add macros to determine IP address length (internal driver types).
This will be used in next patches for nexthops logic.

Co-developed-by: Taras Chornyi <tchornyi@marvell.com>
Signed-off-by: Taras Chornyi <tchornyi@marvell.com>
Co-developed-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: Yevhen Orlov <yevhen.orlov@plvision.eu>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>