net: keystone_net: add Keystone2 K2L SoC support

The Keystone2 Lamar SoC uses the same keystone net driver.
This patch adds opportunity to use it by K2L SoCs.

Acked-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>