ARM: dts: keystone-k2e-evm: Add and enable DSP CMA memory pool

ARM: dts: keystone-k2e-evm: Add and enable DSP CMA memory pool

A CMA memory pool reserved memory node is added, and is attached to
the DSP node through the 'memory-region' property on the K2E EVM board.
This area will be used for allocating virtio rings and buffers. This
node allows the DSP Memory Protection and Address Extension (MPAX)
module to be configured properly for the DSP processor, and matches
the values used on the other Keystone 2 boards for software
compatibility.

The reserved memory node and the user DSP node are also marked okay
to enable the DSP on the 66AK2E EVM board.

Signed-off-by: Sam Nelson <sam.nelson@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>