net: ti: icssg-prueth: Split out common object into module

icssg_prueth.c and icssg_prueth_sr1.c drivers use multiple common .c
files. These common objects are getting added to multiple modules. As a
result when both drivers are enabled in .config, below warning is seen.

drivers/net/ethernet/ti/Makefile: icssg/icssg_common.o is added to multiple modules: icssg-prueth icssg-prueth-sr1
drivers/net/ethernet/ti/Makefile: icssg/icssg_classifier.o is added to multiple modules: icssg-prueth icssg-prueth-sr1
drivers/net/ethernet/ti/Makefile: icssg/icssg_config.o is added to multiple modules: icssg-prueth icssg-prueth-sr1
drivers/net/ethernet/ti/Makefile: icssg/icssg_mii_cfg.o is added to multiple modules: icssg-prueth icssg-prueth-sr1
drivers/net/ethernet/ti/Makefile: icssg/icssg_stats.o is added to multiple modules: icssg-prueth icssg-prueth-sr1
drivers/net/ethernet/ti/Makefile: icssg/icssg_ethtool.o is added to multiple modules: icssg-prueth icssg-prueth-sr1

Fix this by building a new module (icssg.o) for all the common objects.
Both the driver can then depend on this common module.

Some APIs being exported have emac_ as the prefix which may result into
confusion with other existing APIs with emac_ prefix, to avoid
confusion, rename the APIs being exported with emac_ to icssg_ prefix.

This also fixes below error seen when both drivers are built.
ERROR: modpost: "icssg_queue_pop"
[drivers/net/ethernet/ti/icssg-prueth-sr1.ko] undefined!
ERROR: modpost: "icssg_queue_push"
[drivers/net/ethernet/ti/icssg-prueth-sr1.ko] undefined!

Reported-and-tested-by: Thorsten Leemhuis <linux@leemhuis.info>
Closes: https://lore.kernel.org/oe-kbuild-all/202405182038.ncf1mL7Z-lkp@intel.com/


Fixes: 487f7323 ("net: ti: icssg-prueth: Add helper functions to configure FDB")
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Reviewed-by: Sai Krishna <saikrishnag@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>