ARM: zynq: Fix OCM mapping to be aligned with binding on zc702

The commit f6962991 ("dt-bindings: sram: Convert SRAM bindings to
json-schema") converted binding to yaml and some missing required
properties started to be reported. Align binding based on it.

The patch is fixing these warnings:
.../zynq-zc702.dt.yaml: sram@fffc0000: '#address-cells' is a required property
.../zynq-zc702.dt.yaml: sram@fffc0000: '#size-cells' is a required property
.../zynq-zc702.dt.yaml: sram@fffc0000: 'ranges' is a required property
>From schema: .../Documentation/devicetree/bindings/sram/sram.yaml

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/87c02786ccd8d7827827a9d95a8737bb300caeb0.1606397101.git.michal.simek@xilinx.com