soc: ti: k3-navss-ringacc: Add support for native configuration of rings

In absence of Device Manager (DM) services such as at R5 SPL stage,
driver will have to natively setup Ring Cfg registers. Add support for
the same.

Note that we still need to send RING_CFG message to TIFS via TISCI
client driver in order to open up firewalls around Rings.

U-Boot specific code is in a separate file included in main driver so
as to maintain similarity with kernel driver in order to ease porting of
code in future.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210607141753.28796-7-vigneshr@ti.com