arm64: dts: ti: k3-am65-main: Add hwspinlock node

The Main NavSS block on AM65x SoCs contains a HwSpinlock IP instance
that is similar to the IP on some OMAP SoCs. Add the DT node for this
on AM65x SoCs. The node is present within the NavSS block, and is
added as a child node under the cbass_main_navss interconnect node.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>