net: ethernet: ti: cpsw: move set of common functions in cpsw_priv

As a preparatory patch to add support for a switchdev based cpsw driver,
move common functions to cpsw-priv.c so that they can be used across both
drivers.

Signed-off-by: Ilias Apalodimas <[email protected]>
Signed-off-by: Murali Karicheri <[email protected]>
Signed-off-by: Grygorii Strashko <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: grygoriyS