ARM: uniphier: add DRAM PHY clock duty adjustment for LD20 SoC

ARM: uniphier: add DRAM PHY clock duty adjustment for LD20 SoC

If the DRAM clock duty does not meet the allowable tolerance,
it is marked in an efuse register.  If the register is fused,
the boot code should compensate for the DRAM clock duty error.

Signed-off-by: Kotaro Hayashi <hayashi.kotaro@socionext.com>
[masahiro: simplify code, add git-log]
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>