arm64: zynqmp: Remove arm,cortex-a53-edac node

There is no dt schema associated with it. Also Linux driver have been
removed in Xilinx Linux tree and never gets to upstream that's why remove
description for it.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/6685ee980d9b475f95eef6b2a74795adc4ac4619.1706791116.git.michal.simek@amd.com