soc: ti: pruss: Enable support for ICSSG subsystems on K3 J721E SoCs

The K3 J721E family of SoCs have a revised version of the PRU-ICSS (ICSSG)
processor subsystem present on K3 AM65x SoCs. These SoCs contain typically
two ICSSG instances named ICSSG0 and ICSSG1. The two ICSSGs are identical
to each other for the most part with minor SoC integration differences and
capabilities. The ICSSG1 supports slightly enhanced features like SGMII
mode Ethernet, while the ICSSG0 instance is limited to MII mode only.

The ICSSGs on K3 J721E SoCs have two new additional auxiliary PRU cores
called Tx_PRUs in addition to the PRU and RTU cores present within the
K3 AM65x ICSSG instances. There is no change in the Interrupt Controller
w.r.t AM65x. All other integration aspects are very similar to the ICSSGs
on AM65x SoCs.

The existing pruss platform driver has been updated to support these new
ICSSG instances through new J721E specific compatibles.

Signed-off-by: Suman Anna <s-anna@ti.com>