ARM: uniphier: remove DRAM base address from board parameters

ARM: uniphier: remove DRAM base address from board parameters

The base address of each DRAM channel can be calculated from other
parameters, so does not need hard-coding.  What we need is the size
of each DRAM channel and DRAM_SPARSE flag to decide the start address
of DRAM channel 1.

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