ARM: uniphier: fix build error when CONFIG_CMD_DDRMPHY_DUMP=y

The build fails if compiled with CONFIG_CMD_DDRMPHY_DUMP=y since commit
46abfcc9 ("ARM: uniphier: rework struct uniphier_board_data").

Fixes: 46abfcc9 ("ARM: uniphier: rework struct uniphier_board_data")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>