net: ti: icssg-prueth: Add icssg queues APIs and macros

Add icssg_queue.c file. This file introduces macros and APIs related to
ICSSG queues. These will be used by ICSSG Ethernet driver.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>