ARM: zynq: Remove DTC 1.4.2 warnings

DTC 1.4.2 reports these warnings:
Warning (unit_address_vs_reg): Node /memory has a reg or ranges
property, but no unit name
Warning (unit_address_vs_reg): Node /pmu has a reg or ranges property,
but no unit name
Warning (unit_address_vs_reg): Node /fixedregulator@0 has a unit name,
but no reg property

This patch is fixing them.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>