ARM: dts: keystone-k2e: Add PSC reset controller node

The Power Sleep Controller (PSC) module contains specific
memory-mapped registers that can be used to perform reset
management using specific bits for the DSPs available on the
SoC. The PSC is defined using a syscon node, and the reset
functionality is defined using a child syscon reset controller
node.

Add this syscon reset controller node as well as the reset
control data for the resets it supports for the 66AK2E SoCs.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>