ARM: uniphier: rework existing DDR PHY code to reuse for LD11 SoC

The DDR PHY register view of LD11 is slightly different from that
of LD4/Pro4/sLD8, but it will be possible to share the register
macros (and I want to re-use as much code as possible).  Change
the code in the more flexible form.

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