ARM: zynq: DT: List OCM memory

Description OCM with mmio-sram driver. In 99% use cases OCM is mapped high
that's why it is placed on fixed location.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/a951dbe885640197efe3e91bb9fa5caedb54b387.1662460712.git.michal.simek@amd.com