ARM: dts: uniphier: add reference clock nodes
Add master clock nodes generated by crystal oscillators.
PH1-sLD3, PH1-LD4: 24.576 MHz
PH1-Pro4, ProXstream2: 25.000 MHz
PH1-Pro5: 20.000 MHz
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>