net: ti: icssg: Add Firmware config and classification APIs.
Add icssg_config.h / .c and icssg_classifier.c files. These are firmware
configuration and classification related files. Add MII helper APIs and
MACROs. These APIs and MACROs will be later used by ICSSG Ethernet driver.
Also introduce icssg_prueth.h which has definition of prueth related
structures.
Signed-off-by: MD Danish Anwar <danishanwar@ti.com> Reviewed-by: Ravi Gunasekaran <r-gunasekaran@ti.com>