mmc: uniphier: use devm_get_addr() to get base address

Currently, fdtdec_get_addr_size() does not support the address
translation, so it cannot handle device trees with non-straight
"ranges" properties.  (This would be a problem with DTS for UniPhier
ARMv8 SoCs.)

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