arm64: dts: zynqmp: Fix node names which contain "_"

s/_/-/ for node names.

It fixes warnings like this:
... Warning (node_name_chars_strict): /cpu_opp_table:
Character '_' not recommended in node name ...

Issues reported by make dtbs W=12

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