ARM: uniphier: collect clock/PLL init code into a single directory

Now PLLs for DRAM controller are initialized in SPL, and the others
in U-Boot proper.  Setting up all of them in a single directory will
be helpful when we want to share code between SPL and U-Boot proper.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>